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From text near the end of that messege:
"So, what does all this mean? I believe the problem originates with the design of the exhaust system, having the 1st catalytic converter so very close to the exhaust ports. I don't know of any other car that has the 1st catalytic converter built into the exhaust manifold so close to the exhaust ports. The problem doesn't seem to arise until there is backpressure in the system that can cause the precatalyst material to blow back into the engine.
I have not seen anywhere, where anyone has given a practical explaination as to why this is occuring, but this is the most sensible theory that I have been able to come up with. I believe that since the Nissan exhaust system design may have caused the problems with the engine, Nissan should pay the cost of fixing these cars. So I'm ready to jump on this band wagon too."
On the 2.5L 4 cylinder Altima engine, the Pre-Cat is built into the exhaust manifold (one piece). This puts it too close to the exhaust ports, allowing the contents of the Pre-Cat to flow back up into the engine "under certain conditions". The heat shield on the front of the engine covers the exhaust. If you remove the Heat Shield that covers the exhaust on the front of the engine (4 small bolts), you will plainly see what I am talking about. You can plainly see the top and bottom of the Pre-Cat, as there is an Oxygen Sensor at the top of the Pre-Cat, and then there is another Oxygen Sensor at the bottom of the Pre-Cat. There is a 2nd Cat with no Oxygen Sensors farther down the exhaust system under the car before the muffler. The way it SHOULD have been designed FIRST would have been to have the individual exhaust pipes (manifold), come into one common collector pipe that went down to the flexible connection near the bottom of the engine, and then put the Pre-Cat under the car, farther away from the exhaust manifold. This greater distance would insure that the contents of the Pre-Cat would no get blown back up into the engine, eliminating THAT threat to the engine. The SECOND thing that needed to be done was to make the Cat of sturdier construction, so that the contents of the Cat do not leak out. The chemical material is held in place on each end by a screen. The material escapes because the screen breaks, cracks or collapses. It seems like it happens at about 60,000 miles to 90,000 miles, on the reports that I have read, before the screens break and the chemical material is released into the engine. If the screens at each end were made stronger and better, the chemical material would be contained and not destroy the engine.
So Mr Kamikazejoshua, I would take a long hard look at the exhaust system on the 2.5L Frontier engine to see where the Cats are. If the arrangement is like it is on the Altima, you might get the same problems. I have not seen the Frontier, and I have not been on the Frontier Forms, so please let us know what you find out.
Good Luck,
E.D. in Sunny Florida
I would think the the most logical first step that the manufacturer would take is too increase the reliablity of the Converter, by using better screens on each side of the chemical in the Converter, to be sure that the chemical does not get released into the engine, or breaks loose and clogs the exhaust systems at the next component downstream. Hopefully they are doing that allready, but Nissan is remaining silent about this issue. I have been hoping that they would address this issue, but so far nothing. It seems that once it is out of warrenty, you are are on your own. I would suggest if you have not done so, to go back to the begining and read all the posts in this forum, and read all that you can find about it on the Internet.
I expect a car to last a lot longer than the 3 year manufacturer's warrenty, and I expect the Cats to last a lot longer than the 80,000 mile federal warranty. I buy my cars with 90,000 to 100,000 miles on them and drive them to about 200,000 miles, and I still have the original exhaust system, original mufflers, original Cats, original paint, original engine and original transmission that run and shift like new. Thats what I expect, but maybe it's because I drive Ford V8 Explorers. I will buy my next car for my wife this year in a about a month or two, and will likely be a 2004 Toyota Highlander with V6. I will hate to have to sell my wifes 1997 Ford Explorer XLT 5.0L V8, because it has been such an excellent vehicle, but someone else will be enjoying it for a long time. No Nissans for us!
Good Luck,
E.D. in Sunny Florida
I have 3 of these and one affected so far. The other 2 will be up for sale by the end of the winter. I am also going with Toyota or Honda in the future. Glad you have good luck with Fords, I hear from body repair shops that they are slapped together. I guess it it like anything else, maybe the cheaper vechiles are the ones they are talking about. Have you heard anything on a class action filed on Nissan for the Altima's?
I appreciate the info that you've put out on this forum. It has helped me understood technically what my engine problem is. (since I know very little about car mechanics.)
I talked to the dealership service manager recently and this is how I summarized it. The dealership is well aware of this issue with the Nissan 2002 Altima 2.5L engine problem but because Nissan corporate won't do anything about it, the dealerships are pushing cost of repairs to the customers and of course not tell customer's that this is a common problem.
I don't what kind of system Nissan is running but it seems like everyone is on their own, the dealerships are on their own, the customers are on their own, etc. I had no luck with consumer affairs just like everyone else but to be honest, I think it would have been better if they didn't have consumer affairs because they wasted my time. I think Nissan thinks, we will only buy one car in our lifetime. Bottomline, I will never buy nissan, my family will never, my friends and so on etc.
Anyways, I am seeking advice. I am deciding whether to fix my car or trade it in as in a few months from now I am due for new vehicle. The impression I get from your posting and other posting from other people on the internet is that even if I get the engine problem fixed, I will still run into the same problem and because it's just a design flaw with engine. Also, it seems to me that some Nissan dealerships are barely just gettting up to speed with this issue and usually fix one issue instead of fixing all the issues.
I prefer to fix and keep the nissan but if I will run into the same or more problems down the road in the next few months, I will definitely trade it in.
Any info will be greatly appreciated.
thanks,
Isileli
Now to clear up the misconception. I understand how this could be misunderstood by non technical people, because that is who this forum is mostly for. I've worked on cars all my life, I've worked as a line mechanic in 3 american car dealerships in the 1970's and at a national transmission repair chain, but I retired from that work and found a better way to make a living. I still do all my own work however, and maintain a well equipped garage to work in. My prescence here is to help people and give advice if I can. I have been especially angered by this Nissan Altima 2.5 engine problem because it directly involved my daughters car and has costed me time and money (but not nearly as much as most of you). I have heard of the needless problems and pain of the Nissan Altima owners, and I do deeply sympathize with you.
Here is the misconception, many owners are thinking the engine is bad, BUT it is NOT the engine that is bad. It is the EXHAUST SYSTEM that is bad. The Cats are in the exhaust system, and when the Cat goes bad, it ruins the engine by contaminating the engine. If the Cats were made correctly and did not throw their contents into the engine, the engine would probably live a "normal" life. The REAL solution should have been for Nissan to use quality made Catalytic Converters, that would permanently contain the chemical. It may have just been a poor choice by Nissan to use that particular Cat. I don't know where they get them from, and I don't know where they are made, but I hope that they are now using better Cats in the new Altimas.
Once the Cat messes up the engine by throwing the chemical into the engine, which causes the piston rings and clyinders to wear out, then the engine IS BAD, and usually has to be replaced.
The solution to the problem is to NOT let the CAT eat up the engine. This is a touchy subject, because the CAT is required by law, because it reduces pollution. It also depends on where you live and if you are required to subject you car to emissions testing. What happens sometimes is that the chemicals and screens inside of the CAT breaks apart and the contents of the Cat is blown down the exhaust pipe. If the material happens to be blown out the muffler and out the tailpipe, then the material is no longer a threat to the engine, because it is gone. However, since it is gone, the oxygen sensors in the exhaust system, one before the Cat and one after the CAT, will detect that the CAT is not working and will throw the Diagnostic Trouble Code "Catalytic Converter Efficiency below threshold" or some such messege, and will cause the "service engine soon" light to come on. If the CATs get blown out, the engine will run fine, you would have to live with the "SES" light on all the time, if you can.
Last but not least - Don't ever let your Altima engine overheat. The heat will warp the head and blow the head gasket, maybe crack the head, requiring the engine teardown for head gasket replacement and cylinder head rebuild (read messeges #103 - #113).
About the issue of whether to fix the car or trade it in, that is a matter of money, compare the cost of repair and aggrevation against the trade in value. Unfortunately, I think you lose either way, it's just a matter of how much you lose. Only you can decide how to spend your money.
Hope this helps,
E.D. in Sunny Florida
You say its an 02, which would make it just barely 6 yrs old. Is it still under warranty? even if you bought it used, most of the extended warranties transfer to the next owner.
anyhow, find yourself a good mechanic who knows how to properly diagnose a car.
my advice would be to take it to a garage that specialized in foreign cars, or another nissan dealership. It's most likely something in the electrical system, and electrical problems are a pain in the [non-permissible content removed] to track down.
I have read your original messege #174 and all the following messeges to date, 175 through 180. I have not checked in here for a couple of days. I am a semi-retired mechanic, and I just just did major rebuild work on one of these same 2002 Altima 2.5L 4 cylinder inline engines in December 2007, my daughters car with 100,903 miles on it. It had all the typical problems that we are seeing in some of these cars today, such as problems with the catalytic converter failing and/or plugging, begining to use more oil problem and leaking head gasket problem. I fixed all those problems and now her car is running perfect every day. I am familiar with this engine and all the sensors. Looking at the original information and the following comments, I see a lot of holes and/or gaps in the information about your car. The reason that the several mechanics have not been able to fix your car is because something is being overlooked. We need to go back to the basics and start from the begining and work our way through the problem to find the solution. I will be able to help you by steering you in the right direction if you can just give me the correct information that I need, and fill in the blanks or gaps. The better information that you can give me, the better I can help you.
First, you need to be familiar with what is going on with this engine, the problems that are showing up and why the problems are happening. It may sound far feched, but your engines problems are likely related to these problems that have been discussed on this forum so far. If you have not done so, please read all the messeges in this forum, or at least messege #75 on to this one.
Here are a few questions to get started. Please gather up all the information that you can and reply back with your answers. I'll check back in a couple of days.
1. What were your original complaints that led you to think anything was wrong with your car? Having to add oil frequently? Engine misfiring or running bad? Subsequent compaints or anything else? Is the current milage about 116,000 miles?
2. You stated that "I have had unexplained oil consumption". But no further comment has been made about that. Since the oil consumption is "unexplained", I would assume that there is not an oil leak anywhere on the engine after the valve cover gasket was replaced. How much engine oil is the engine losing in 1000 miles? How often do you check the engine oil level? How often are you having to add engine oil, and how much? If you don't know exactly, try to give an estimate.
3. Then you brought up the problem of misfiring on cylinder #3. Was misfiring an original complaint? How was the misfiring determined to be on cylinder #3? Did the technician read the DTC's (Diagnositic Trouble Codes) with a Scanner? Find out what codes were scanned and please report them here. Tell me all you can about this misfire. Does it happen all the time or just some of the time? Does it miss when you first start the engine after it has been sitting for a long while or over night? Does the miss go away after you drive it a short distance?
4. Have you had a noticable loss of power from the engine, and if so, did it seem to ocurr suddenly or over a period of time? Have you had any known problems yet with the Pre-Catalyic Converter or the Catalytic Converter, or had any trouble codes pertaining to them?
5. You were also told "no water coming through". I would assume that is referring to any coolant leaking inside the engine. Has the engine ever run hot? Have you had any instance where the engine got hot because a hose blew or the radiator blew? Where does your temperature gauge normally register with normal driving down the road (Normal is in about the middle of the temperature gauge). Does the temperature gauge vary very much once it is warmed up? Does it read at about the same when sitting at a light with the motor idleing? Check the coolant tank reservior tank level often when the engine is cold. Does the level of coolant in the coolant tank reservior stay the same level, or does it go low. Do you have to add any coolant to the coolant reservior? It is normal for the coolant level to be lower when the engine is cold and higher when the engine is at operating temperature.
Your mechanic should have a handheld scanner that is capable of monitor mode, being able to see and read the functions that the computer monitors, such as coolant temperature, ignition timing, intake air temperature, intake air volume, fuel trims, oxygen sensors, etc. He can have this connected to the car and observe these things while the car is stationary or while driving the car. With the car stationary and engine idleing, the coolant temperture should rise up to about 200 to 203 degrees, then both the electric fans behind the radiator should come on, then the temperature should drop down to about 188 degrees and then the fans turn off. This cycle continues, but when moving down the road, the fans may not need to come on because of the wind blowing through the radiator.
6. You said "Was told that the piston is fine, no scoring, no water coming through. Compression is fine". How were these things determined? If the compression was tested on the cylinders, it is important to know what those are. My daugthers 2002 Altima 2.5 had 190 pounds of compression in each cylinder, which is very good. This indicated that the pistion rings were good and holding compression well. Also good is the fact that the compressions on all 4 cylinders was the same. The maximum compression variation between cylinders is 20%, which in this case would be about 38 pounds, so the acceptable range of compressions should be about 152 to 190, the closer the better. Howerver, compressions alone are not the sole indicator of engine condition, all factors must be considered together to arrive at the proper conclusion. In the case of my daughters Altima, even though the compressions were good, the head gasket was still bad, because it had a very small leak in the head gasket that allowed coolant to flow into one cylinder when the engine was shut off. When it was restarted from a cold start, the coolant in the cylinder caused that cylinder to miss for about a minute until the spark plug dried off and started firing, then it ran fine. The problem was found because the coolant reservior ran low and combustion gas was found in the radiator.
7. Referring to the scoring, how was it determined that there was no scoring. The only sure way to tell is by taking the engine apart, removing the cylinder head and examining the cylinders. Other that that, it may have been assumed that the pistons were ok and that there was no scoring due to good compression readings.
Continued on next messege
8. Since you have taken your Altima to the dealer to be checked, I would assume that they put in the Recall with the updated Crankshaft Position Sensor and the updated Camshaft position sensor. Is this correct? I would also assume that they did the Recall for the Intake Manifold Power VaIve, where the upper intake manifold is removed and the power valve screws are checked and tightened. I would check and verify if these recalls been done, and let us know.
9. You said "Then my Piston # 3 was misfiring. I had my #3 coilpack and plugs replaced. Piston #3 kept misfiring. Was told by another mechanic that I should have had a Nissan coil pack and platinum plugs put in. I did that. Piston #3 still misfiring".
What was the condition of the original spark plug on #3 cylinder? Fouled? Dirty? Wet? Oil? Coolant? Were all 4 spark plugs replaced? If it is still missing, all 4 spark plugs should be carefully removed and looked at. The condtion of each one should be noted. They should be clean and dry, light tan in color, electrodes not bent, all look the same.
That is enough questions for now. Please gather up what you can and let us know what you find out.
If you or anyone else would like to see pictures of the 2002 Altima 2.5L engine being taken apart and put back together, I posted links below that can take you to the photos. The site is for photographs of all types, and the basic service is free, pictures can be stored on albums there for free. They only charge if you buy photos from them. If you are not registered, you can simply register to gain acess to viewing the pictures. There are hundreds of photos of taking the engine apart and hundreds of photos putting the engine together.
2007-12-10 2002 Altima eng teardown pictures
http://www2.snapfish.com/thumbnailshare/AlbumID=215829101/a=85874609_85874609/t_- =85874609
2007-12-17 Altima eng rebuild pictures
http://www2.snapfish.com/thumbnailshare/AlbumID=215829106/a=85874609_85874609/t_- =85874609
Good Luck,
E.D. in Sunny Florida
1. My original complaint was no heat at idle and some hesitation at 40MPH. Had heat issue fixed, plug 3 oil fowled. 116K miles on car.
2. Had gasket under valve cover replaced (leaking oil). Was losing about 1qt. oil every 1000 miles. Haven't had any loss of oil since gasgket replaced. I was checking my oil once a week.
3. Misfiring on cylinder#3 started about 2 weeks after orig. issue. Had codes read and Cylinder#3 misfire detected. This is the only code that comes us. Had o2 sensore checked and was fine. Then had platinum plugs and new coil pack installed. It only happens when I reach 40mph. Although, two mechanics had it for a day or two and they said it didn't happen. Some times it can go a day before happening - only after driving it a while. It never happens after first starting the car. Now when cylinder#3 misfire is detected, the plug are carbon fowled - not oil fowled. Had my ecm reprogrammed at dealership along with other recalls (headlamps, erar subframe, fuel screen)
4. There has been no loss of power. I have not had any probs. w/catalytic convereter (as far as I know).
5. The mechanic just told me that no water came through piston #3. The heater gauge has never varied from the middle of the gauge. Coolant seems to be just fine in resevoir.
6-7. I really think the mechanic was just assuming that there was no scoring etc on piston #3. The compression of all cylinders is 150.
8. The dealer never told me about recalls on crankshaft position/sensor or the Intake Manifold Power Vavle. I will call them - thank you.
9. The condition of the plug (3) was carbon fowled.
today, they are re-dagnosing (I hope) my car and will post the results as soon as I hear something.
THANK YOU so much for all this helpful information. I really appreciate it. I wish you lived up here!!! I really need someone who knows what the heck they are doing!!!
It is very good that your engine oil consumption/leak has stopped and that you have had no catalyic converter problems, but please be very aware of these problems, because if the catalyic converter goes bad, it will mess up your engine. Still no oil loss? It is also good that you have had no loss of power and no loss of coolant.
The original complaint of no heat is a common one for this car, the heater circuit gets air trapped in it and therefore no hot coolant flows through the heater core. The solution to that is to purge the air out of the cooling system.
There was some conflict between items #1, #3 and #9.
In #1 you said "plug 3 oil fowled", and in #3 you said "the plug are carbon fowled - not oil fowled" and in #9 you said "The condition of the plug (3) was carbon fowled". So I guess you meant to say that the plugs are dry black with dry carbon on them, not wet black? If that is so, and it is only occuring on that one plug, then the problem is obviously related to that cylinder. Since it is dry carbon, I would first suspect a RICH FUEL MIXTURE. The most likely cause of this is a bad fuel injector, causing more fuel to go into that clyinder. It can cause the fouled plug and could be the source of the engine miss. The fuel injectors are difficult to see or reach, as they are "trapped" under the upper intake manifold. Once the upper intake manifold is removed, they are very easy to reach. Two small bolts hold the fuel rail on to the lower intake manifold. The fuel injector wiring plug is unplugged at the passenger side of the engine, the two bolts holding the fuel rail are removed (don't lose the 2 spacers under the fuel rail, one at each bolt), and then the fuel rail with the injectors attached can be gently pulled from the lower intake manifold, then the fuel injectors can be replaced, use new seals lubricated with a little oil when putting them gently back in. A good prevention for this problem is to put a bottle of fuel system cleaner or Gas Treatment in your gas tank at every oil change. This should be part of every service for every car. When the Upper Intake Manifold is OFF, be SURE that the POWER VALVE SCREWS are checked to be SURE they are tight, there are 4 valves, 2 phillips head screws on each valve. They are plainly visible and accessable only when the upper intake manifold is off.
2. Review the following cleaning recommendation for the intake and exhaust systems when you replace, repair or check an engine:
^ Visually inspect for debris, water, or other foreign material inside the entire intake system, from the air filter intake through the intake manifold; clean as needed.
^ Inspect the intake manifold "runners" from the cylinder head side. Make sure that no particles of metal (broken pieces of piston, valve, etc) have stuck to the walls of the runners.
^ Visually inspect the "flange" portion of the manifold, where it attaches to the head. Make sure there are no scratches or burrs that might cause a bad seal seal.
^ Visually inspect the "power valves" inside the intake manifold (if applicable). Make sure all retaining screws that attach the "butterflies" to the shaft are in place and tight.
^ Make sure the exhaust ports are clean and free of debris.
^ Inspect the entire exhaust system for debris or other foreign material. Clean or replace as needed.
Another reason for the plug fouling black could be a weak spark. Even though they have replaced the coils, I would have them check the strength of the spark, by comparing each spark against the others. They should all be able to make the same length of arc. A weak sparks means a weak coil or a problem in the circuit.
Another reason that the fuel injector may flood the clyinder (much less likely), is the computer sending it the wrong signals, due to a computer or sensor malfunction. That is why you want to be sure that the voluntary sensor recall was done on your car. The recall covers two different sensors, the camshaft position sensor, shown photos #07219 and 07335, on the drivers side of the cylinder head, and the crankshaft position sensor, no picture, located on the back side of the engine. The replacement parts come in a kit called QR25DE sensor kit P/N 23731-6N225. Both parts look identical, but they are NOT, the Crankshaft Position sensor has a white paint mark on it. Do not mix up the parts.
Date:
December 19, 2003
VOLUNTARY RECALL CAMPAIGN ENGINE SENSORS
CAMPAIGN I.D.#/NHTSA #:
R3022/03V-345
APPLIED VEHICLES:
2000-03 Sentra (B15)
2002 Altima (L31)
2002-03 Maxima (A33)
2003 Murano (Z50)
2003 350Z (Z33)
The compression on the cylinders (150) sounds low, but depends on how it was done. Are they sure that they were all the same? Verify how they were taken, if you can. All plugs out, battery charger on the battery to keep it charged up during the test, Throttle valve on the intake plenium blocked open, test one cylinder at a time at full cranking speed, using a good quality screw in compression tester. I was expecting 170 lbs per cylinder or more. As I said, my daughters 2002 2.5L tested at 190 in each cylinder at 100,900 miles. After the head was milled and the engine put back together, they all tested at 205 to 210 lbs per cylinder. 150 may work, but a higher compression indicates a healthier engine. Your numbers may be low due to how they did the test.
That is enough for now, getting late,
Good Luck,
E.D. in Sunny Florida
Hope this helps you.
Please read the previous messeges in this forum to understand the nature of the complaints and possible solutions.
I am sorry to say I can't help you, I want to help you, but it sounds like your engine is too far gone, but check a few more things.
There might be one more thing to check, since you seemed to notice improvement when you changed the PCV valve, there just may be a small possiblity that the oil could be getting sucked up by the PCV valve and the oil gets burned up in the engine and goes out the exhaust. 5 quarts of oil is all the engine holds, so you use a tremendous amount of oil for such a short time. How many miles do you goes in this 2 days and is it highway driving? I would check the PCV valve again very closely to be sure the oil is not getting sucked through it. At this moment I can't remember exactly how the hoses all went, an I don't have time to look at the pictures, but you could trying pulling the PCV hose and vent hose off the engine while it is running to see if you see "blowby" (pressured gas or smoke) coming out of the engine crankcase. That could be a sign of piston ring failure. If you see no blowby, then it just might be the PCV valve sucking oil out of the engine. If so you could trying leaving the hose off the PCV and driving to like that to see if it stops using oil. Watch it very carefully and check often to be sure oil does not leak out. If you are not sure about how to check the PCV, have a mechanic check the PCV and also check the engine crankcase for any blowby. If blowby is found, check cylinder compression to verify the engine condition. Test the compression on each cylinder, as I have outlined in previous messeges. If the results are very low, under 150 lbs in each cylinder, I would think you have a serious problem with wear in your pistons and rings and cylinders. If the compressions are NOT LOW, then there may be hope for your engine yet.
I may check into the possibility of the PCV causing this, but I do not get acess to the car very often, I will check the pictures later, but may not be able to tell much by them. If I find anything that could appear like it may cause this to happen, I will address this later after I have all the facts. This would be a very unsual problem, but may be worth looking into.
If you do have heavy wear in the piston and cylinders, you will need another engine, because if it uses that much oil that fast and not leaking and low compression, that means your pistons and piston and cylinder walls are all worn out. They have been eaten up by catalytic conveter spewing it chemicals into your engines exhaust ports, Once the engine parts are eaten up by the abrasive chemical, the engine is destroyed. It's like if you ate sand all the time, how long would you last?
Check that PCV. Have you read the previous messeges? Particularly #169, I spoke about what the problem was and what to do about it. Unfortunately, you have to do somethihg about it early on, before it is too late.
Below is some key text from that messege. It says what to do about the problem and how to avoid having the problem, but you have to read between the lines, Everyone with the 2.5L engine should read this:
The solution to the problem is to NOT let the CAT eat up the engine. This is a touchy subject, because the CAT is required by law, because it reduces pollution. It also depends on where you live and if you are required to subject you car to emissions testing. What happens sometimes is that the chemicals and screens inside of the CAT breaks apart and the contents of the Cat is blown down the exhaust pipe. If the material happens to be blown out the muffler and out the tailpipe, then the material is no longer a threat to the engine, because it is gone. However, since it is gone, the oxygen sensors in the exhaust system, one before the Cat and one after the CAT, will detect that the CAT is not working and will throw the Diagnostic Trouble Code "Catalytic Converter Efficiency below threshold" or similar messege, and will cause the "service engine soon" light to come on. If the CATs get blown out, the engine will run fine, but you would have to live with the "SES" light on all the time, if you can. Can you?
About the pictures of the teardown and rebuild of the 2.5L engine, I posted the links to both sets of those pictures at the bottom of messege #182.
ANYONE can view those pictures. All you have to do is click on the link in the messege and it takes you to the photo album at the site. All you have to do is log in to the site (you will have to register, if you haven't before, it's free), it will automatically take you to the photo album where you can view the photos individually, view a slide show for free or buy prints of any that you may want. There are over 300 photos in each set.
If clicking on the links does not work on your computer, copy and paste the link to your browser and click GO, to get to the photo site.
Good Luck,
E.D. in Sunny Florida
"Initially, plug 3 was oil fowled due to a minor leak through the valve cover gasket".
I am not aware of any way that a valve cover gasket leaking could allow oil to get into any cylinder or combustion chamber. They are simply not related.
I assume the mechanic just switched the ignition coils between cylinders #3 & #4 and the same problem occured? The problem may be the primary circuit feeding the coil, which comes from the computer. It could be the connector is bad, or the wiring is bad, or an input to the computer is bad, or the computer could be bad, in that order. HOWEVER, I would be sure to test the output of each coil first, just like I said in my previous messege. If the coil is putting out a weak spark, whether it is the coil, wiring, or computer, it will show up in the coil output voltage test. You can compare the relative voltage output of each coil by the maximum length of the spark it makes.
Here is how I do it.:
To test the coil output voltage, you test one coil at a time. The engine is going to run on 3 cylinders while you test the fourth coil. Remove the small bolt that holds the coil in place. Unplug the connector from the coil and pull the coil up off the spark plug and out of the valve cover. Plug the coil back into the connector. Place a good insulator under the coil to hold it up off the engine (like a dry block of wood). Make sure the coil has the long boot on it that goes down to the spark plug. Get a good flexible test wire with an alligator clip on each end. securely fasten one alligator clip to a GOOD Ground in the engine compartment. Be sure that it won't come off. If it comes off while you are doing this test, you will recieve a tremendous shock! So be sure it stays on. At the bottom of the coil boot, insert a piece of wire or rod or screw that when in place will connect to the metal inside the boot and act as a conductor protruding a short distance out the end of the boot. Clip the other end of the alligator clip test wire to this metal. When all set, have an assistant start the car, keep yourself and wires away from moving parts. The motor will run a little rough since it is running on 3 cylinders. Carefully loosen the alligator clip from the metal protruding from the coil boot, and slowly withdraw the alligator clip away from the metal. It will draw an arc, should be bluish-white with some some tinges of red or orange color. Continue to slowly draw the arc longer and longer, noting how long it is before the arc starts to fail. Measure with a WOOD ruler if you need to. Clip the aligator clip back on the metal and have the assistant shut off the engine. Write down the arc length and cyinder number. Remove the test wire and metal and assemble the coil and plug back into the original correct position and install the small coil bolt.
Do this same procedure on the other coils and compare the arc lengths. The longer the length, the higher the voltage. they should all be about the same are length. Any coils found with short arc lengths should be investigated for weak coils or problems in the primary circuit.
What's this about a remote starter? I had not heard you mention that before.
Did your engine have all the sensor recalls done to it?
Good Luck,
E.D. in Sunny Florida
The crankcase vent hose (the hose that carries clean intake air into the engine crankcase) on the drivers side end of the valve cover, is shown in photos #07364, 07365 & 07366. Remove the spring clamp as shown, and pull the hose loose from the valve cover. You might have to take the other end of the hose loose, to get enough slack to pull it off the valve cover.
The PVC suction hose (the hose that carries the dirty air, fumes or smoke from the engine crankcase to the intake plenium) connects on the back of the valve cover, is shown in photo #06958, you loosen that spring clamp and pull that line off the backside of the valve cover. When you pull the hose off, the hose should have suction when you start the engine, plug the hose. Look to see if any smoke comes out where you unplugged the hose from the valve cover. Having both hoses disconnected will expose the crankcase to atmospheric pressure, and it any smoke or pressure is created by blowby, it will come out one or both of the openings. A very small amount of blowby is acceptable, but a large amount is not. Having someone rev the engine may increase the smoke, if any is visible. If you do get a lot of blowby gas coming out the valve cover opening, it is an indicator that the piston rings are worn out, but confirm with a compression test. You can also do a vacuum test, but the clyinder compression test give more reliable results.
I would not tear into or rebuild the engine without making a thorough diagnosis first, to be sure of what is wrong with it. If you are going to rebuild the engine, you will have to remove the engine from the car. It may be best to buy a remanufactured engine and put one in. A remanufactured engine from Jasper Engines with a 3 year warrenty is $3,411.00.
You said "My intentions are to rebuild if possible or to buy another engine, but in doing this should we expect the same problems in the next 100,000 miles. Has Nissan done anything about the top cat, or should we all expect it to malfunction again. If not, it seems a fresh rebuild or new engine would be a complete waste of time and money", and you are right, you will have the same problems again, because the problem is NOT the engine, the engine is a fairly good engine, The problem IS the PRE CATALYIC CONVERTER failing and contaminating and destroying a perfectly good engine. Nissan has not done anything about the pre-cat as far as I know.
Listen closely, read all the messeges in this forum so that you know what is going on. If you are really looking at spending that much money and that much inconvenience, it is certainly worth doing a days worth of research so that you can avoid this problem in the future. I gave you the solution in messege #190, read the BOLD TEXT again, and this time read between the lines. The catalytic convertors are required by law, so I can't legally tell you to change, alter or modify them. I can only tell you what I did. What you do is up to you. But I have permanently solved the catalytic converter problem on my daughters 2002 Nissan Altima 2.5S. It is running perfectly fine now. She has drove it about 1500 miles since I put the engine back together, and it is smooth as silk, no smoke, not using hardly any oil (she said the oil was barely down from full on the stick). Also, it is important to go back and read messege #75, and pay special attention to the part that says:
"When I felt the 2nd catalytic converter, it was still cold, even after the engine ran for several minutes. That means it was plugged up! I unbolted the pipe and 2nd catalytic converter and took it off and unplugged it, put it back on, and the car ran perfect again."
I fixed the converters, and I don't expect to have any converter problems or oil burning problems with it. Her converter problems were not as bad as yours, and I caught the problem in time BEFORE it destroyed the engine. Her car was starting to use about 1 quart in 1500 miles, but now it seems a lot better, will know by next oil change. I was fortunate that the Cat Plugged up the exhaust system, which brought the problem to my attention. I then unplugged the cats and the problem is gone. The reason her engine had to come apart was because the head warped and the head gasket began to leak. I removed the head, did a valve job on the head, milled the head flat, put on a new head gasket and put it back together. Take a look at the pictures of the pre-cat, photos # 06930, 06931,06932, 06933 & 06934. The inside of the pre-cat are gone, they blew down the exhaust pipe to the second cat and plugged it up. She is taking the 2002 Altima 2.5S on a 400 mile trip tomorrow, mostly interstate driving, so I will see how it did when she gets back.
The following link is to the album on the photo site that has the photos of how the cat (second cat, the one under the car right before the muffler) was unplugged:
http://www2.snapfish.com/thumbnailshare/AlbumID=215914481/a=85874609_85874609/t_- =85874609
Photo #06065 shows the the second cat, the one under the car, the one that plugged up. Photo 06064 shows it in front of the muffler. Photos 06068 & 06069 show a lot of water draining out of the muffler, it was FULL of water because barely any exhaust gas went through the converter, and what little did condensed into water in the muffler, because the muffler never warmed up. Photo 06082 shows a close up of the second cat off the car. Photo 06087 shows the inside of the second cat before it was unplugged. Photos 06096 & 06097 show the stuff that came out of the cat when it was unplugged. Photos 06098, 06099 & 06100 show the inside of the second cat after it was unplugged.
I have gone into a lot of detail in explaining these problems, because in this open forum setting, many others will read these messeges and hopefully many will benefit from them.
Good Luck,
E.D. in Sunny Florida
If I were you, I wouldn't worry about it. Though the problem does exist, its not affecting anywhere near a majority of altima's. The chances of lightning striking twice would seem pretty rare to me. but, if your not comfortable with it, I'd sell now rather than waiting.
I also am somewhat anxious about some of the posts written here but of the millions of Nissans on the road, I think it is worth the gamble to buy the vehicle. We are reading about such a small cross section of Nissan owners that the number may well be well under .01%. The car drives great, fuel economy promises to be very good, the seven year warranty we purchased should pick up most of the problems, and you will look good in the car. Check out all the threads involving the Altima and then go look at them at the dealers with any questions you have. Also check out the reviews on the 2008 Altima just to the right on this page. Lots of info there.
Hope this helps and good luck in whatever you purchase.
The Altimas themselves are lovely cars and are fun to drive. My daughters 2002 is a dream to drive, she really loves it. I think almost everyone who drives them loves them. It's just the people who have problems with them get disgusted with them, but who can blame them? Since I fixed the engine in my daughters 2002 Altima, it is again a dream to drive. It was a really nice test drive after I put the engine together, I spared it no mercy, slammed it through the gears, blasted to over a 100 mph pretty quick for just a little 2.5L engine! It drives great and handles great. They are great cars, its just a shame that some have these problems.
I have been researching the problems with the engine, trying to figure out what the problem is or was, and this research has been ongoing, even until now. I started researching and thinking about this since September 2007, when the cat clogged up on the 2002, and I unplugged the cat. Then I went on to therorize how the oil consumption problem was related to the cat converter failure problem, and they definitely are related. Then I had to tear down my daughters 2002 in Dec 2007 due to head gasket leakage, to replace the head gasket and repair the head. I think that the head gasket problem had to do with the engine overheating more than anything else. But in the process of repairing the engine, I made sure the cats were all unplugged, and they have not been a problem since then. It seems that the oil burning is greatly reduced (I will be able to confirm this in a few months). My daughter is driving it every day, and says it's running great. My thoughts at this time is that the real problem was not in the engine, but in the defective cat, which then causes the problems in the engine. In taking the engine apart and putting it together, I was quite impressed with the design of the engine, and it seems to be built to be quite reliable.
I have also continued my research looking at other make and models of engines, and found that the other makes also use the same type of layout and design of the exhaust and cats, and are not having these problems, which further leads me to believe the oil consumption problem in the Altimas was due to bad cats, cats deteriorating, and NOT from bad design. So it seems to me that if the cat is good and does not break down, the engine should last a long time, a normal lifetime. So hopefully Nissan took note of the problem and is putting better cats in the newer cars. The only thing is, the problem will not show up until much later, if it shows up at all. Time will tell.
In summary, I think if you buy a new Altima and drive it for a few years, and then trade it in, you should be fine. I think the main concern should be for those used car buyers who are in the market buying 5 or 6 year old cars out of warrenty with about 80,000 or more miles on them. They may not be aware of the problem and buy the car, and then have the engine go out shortly thereafter, a very unfortunate disaster for a young hopeful buyer.
Good luck and happy driving,
E.D. in Sunny Florida
different people have different opinions and experiences when it comes to reliablitly, but this is my third nissan product. the first one, a sentra, lasted 220k miles with no major repairs, and was traded in still running. My second, a 1998 200sx, has 151k miles, I still own, is still running, and I drive it to and from work (about 50 miles per day) four days a week. in the 10 years I've owned it I've had to put 2 sets of front brakes on it. Thats it. brakes twice in 10yrs and 151,000 miles.
those two nissan vehicles are the reason I bought my altima over a camry, accord, or other mid size.
I just bought a 2002 Altima in january with 90K miles and in the first week heat stopped working.......after 3 weeks i had the engine problem and thank god i had the extended warranty so they changed the whole engine.........now i am in a doubt.... should i keep the car or not? ............any suggestions.....please help
Thanks once again