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I think a problem here is that people wander on to this site and read a message or maybe a few, draw some short conclusions, and make a comment , without really knowing the facts and doing the research. All the answers to what you need to know ARE in this forum, they have been posted over and over again. Please do some research and look for them. You read my post about how I hollowed out my cats, and you just assumed that you should too. Wrong. I hollowed my cats out for a good reason, because they NEEDED to be hollowed out. Few people have that need. Please go back and carefully read posts # 75, #76 & #77, and you will find out why I had to hollow out both my cats & what you need to do. In fact you should go back and read all the posts before yours, as they contain a wealth of information, including the $5 O2 Cheater, how it works and how to install it.
Good Luck,
E.D. in Sunny Florida
Yesterday I had a dealer check it out and they found the pre-cat was "coming apart internally" and replaced it under warranty. Hopefully, none or very little material made it into the engine; I'll be keeping watch for oil consumption and hope that any problem with that shows in the next 30K or 2 years while the drive train warranty is in effect.
So, either the pre-cat was just a bad part or the '02-'03 recall situation will be continuing as all 2.5 reach higher mileage.
Anyone know if or what changes were made for the 04-06's at address the failure of the pre-cat? I'm thinking none other the the ECM re-programming to maybe lean out the engine.
Chris
that's all it really needs. the cat wont deteriorate without gas igniting in there. The problem isn't a faulty cat, or a faulty engine. its unburned gas burning in the cat and tearing it apart. You took your car in as soon as that light came on, a very smart man. unfortunately, most people dont. most people figure they left the gas cap too loose or something, and don't want to spend the $80-100 to get the code reset.
First, unbolt the upper manifold and Plenum (all one piece).
Second, unbolt the lower intake manifold from the back of the engine. There is a bracket under the lower intake that has to be removed.
To see all the pictures of how to take it apart and put it together, look at the links in messege #182.
See Teardown Photos #DSC06971 through DSC06980, and see Rebuild Photos #DSC07265 through DSC07270.
Good luck,
E.D. in Sunny Florida
My question is since the emission is not checked where I live is it better to remove the CAT?
Thanks Onuchukwu Chuma.ndiboy@yahoo.com
2348033974181.
I was expecting to see this cat stuff in one bit, but to no avail.One thing that is not clear to me is the whitish brown material in the container.Is it the stuff that is blocking the exhaust? Then there is another hole there, probably after the plug was removed, please I need more clarification now that I have seen the pics.
The pre cat, I must confess i didnt see it.I tried looking into the manifold when it was lowered but i couldnt identify anything I could call the cat.I thought the cat will be something big that I will easily see.
I need these things to be clear because I will like to remove the one in my Altima 2002 car,especially the pre cat,early before any problem starts.Mine is around 76,000miles now.
ED,I need early and fast response,thanks and God bless you.I want mine to run like your daudhters car!!!!!! I love the car,stay in Nigeria, so if the car develops a problem,it gonna be terrible.
Chuma.
I'll be glad to help clear things up. Yes, you have a good Idea to remove the pre cat before the problems start, especially since you don't have emissions inspections.
The best way to refer to the pictures is by NUMBERS, since there are about 700 pictures or more.
The pre cat is built into the exhaust manifold. The top of the exhaust manifold, as it is being removed, is shown in teardown picture DSC06900. The bottom of the exhaust manifold is shown in teardown pictures DSC06930 through DSC06934, it shows views looking up inside the bottom of the exhaust manifold. Normally you would see the precat there, but in those pictures it is gone, the exhaust manifold is EMPTY. If the precat was there, you would see a screen in the bottom that holds the precat material above it. In this case the screen failed and the screen and all the precat material got blown out of the exhaust manifold and was blown down the exhaust pipe into the SECOND cat. When the material got blown down to the SECOND cat, it plugged up the second cat. That is when I had to remove and unplug the second cat. And yes, that brown and whitish material IS the contents of the SECOND cat plus the contents of pre cat. What happened now is that both cats are hollowed out, the pre cat and the second cat, giving a wide open exhaust, of course it still goes through the muffler, like a regular exhaust.
Looking at the unplug cat photos, photos DSC06096 & DSC06097 show the old cat material that was removed from the second cat. This contains the material from the pre cat (first cat) and second cat. Then photos DSC06098 through DSC06100 show the hollowed out inside of the second cat after the contents have been removed.
Photo DSC06087 shows the inside of the second cat BEFORE the contents were removed, the cat is plugged in this picture. What you see is the screen that holds the cat material in place, but the material had got wet and compacted, and the exhaust gas could not flow through it. The cat normally works by allowing the exhaust gas to pass through the cat material and then through the screen and then on to the muffler. The purpose of the screen is to hold the cat material in place. Once ithe cat pluggs up, it's no good anymore unless you unplug it or replace it. Unplugging the second was fairly easy once I had it off the car, just use a hammer and a metal punch or small diameter piece of pipe to hammer the stuff out.
If you look into the bottom of the pre cat, you should see a screen just like in photo DSC 06087, unless the material has already blown out. You could clean out the pre cat the same way, break the screen and material out with a piece of small diameter pipe and a hammer. I think you should be able to hollow out the pre cat from under the car by removing the exhaust pipe and breaking out the material through the bottom opening, but be careful to not damage the oxygen sensors. It is best to remove the second oxygen sensor before you attempt to break the material out of the pre cat. You can run the engine for just a few seconds to blow the loose material out of the precat. After the pre cat is hollowed out, the service engine soon light will come on shortly thereafter, because the SECOND oxygen sensor will read the SAME as the FIRST oxygen sensor. To avoid this, you will need to add the O2 cheater at the SECOND oxygen sensor to make it read differently and for the light to stay off.
Hope this helps,
Good Luck,
E.D. in Sunny Florida USA
You mean the hollow in the cat unplug pics DSC06098-100 is all that the exhaust gas needs to move out?.
Before I go further, I want to let you know someother things.I have been really afraid for this car because before and since I bought I have been reading a lot about it, Camry and Accords on the net, reviews etc The reviews have been that of mixed feelings for all the cars so I decided to go with this with this innate fear.The engine looks new and clean for a 73,000miles car so I was wandering is this not one of those the engine has been worked on and sent to Nigeria?.
One sunday morning,about 2 months ago, I started the Car and after some seconds i heard a sound like something has dislodged inside the bonnet and i thought it was the cat since I have read several reviews of it coming off and damaging the engine.I was already looking foward to the engine dying but the noise stopped as if the stuff has dislodged and off we drove to church and till now nothing has happened.I change the oil every 3months with 4litres, and the filter every 6months and the oil level remains the same.
Is there a way of knowing if the pre cat has been removed? Do they remove it before sending the cars to Nigeria?
When I bought the car, the service engine light was on and I complained because of the reviews I read on the net about it.Later since it was not giving any problems and many cars down here show that, I ignored it.I changed the oil and filter, it still remained but after taking it out on a journey of about 500km I noticed the SES light has gone off.It remained off until about 3 mths later when it came on.I always turn the fuel cap several times after refuelling.I serviced it again ie changed the oil,the light remained.Now I travelled again about the same distance as the previous one and noticed that the SES light has gone off again(2weeks ago), and has remained off till now.My question now is can one use the light to gauge when to change the oil?
I am presently on a cross country journey in the Niger Delta area and will be here in the next one month so I will try and remove the pre cat when I get home.
Since you said the engine is good when you had a look at it,will you recommend it for somebody? since every car has its own fault.
The noise I heard that sunday,can it be the pre cat dislodging?My only observation is that when the car is idling, if you rev it there is a little drag between the idle tachometer level(0.5) and 2.0, but its not felt when the automatic gear is engaged.You know this car so much that If I were in your position, I will erk out some living from it.
Thanks for your concern and prompt response, its highly appreciated and looking foward to response to the questions raised above.
Chuma.
Q. "Pics DSC6932-34 contains a whitish ring like a loop opposite the O2 sensor ,I wander what that is."
A. There are two whitish rings in picture DSC06932, they are the outer ring support for the screens. The lower screen ring is in place just above the oxygen sensor. The outer ring is all that is left, the screen is blown out, missing. You can also see the upper screen ring, with missing screen, it has blown loose and is visible at an angle. It is suppose to be out of sight farther up at the top of the precat, but because it has blown loose, you can see it in the picture.
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Q. "You mean the hollow in the cat unplug pics DSC06098-100 is all that the exhaust gas needs to move out?"
A. No, that is the SECOND CAT hollowed out. I needed to hollow out the second cat because it became totally plugged up. Your first priority is to hollow out the FIRST CAT (the pre cat), that is where the problem arises that destroys the engine. Your second cat is probably ok If the second cat is not plugged, I would recommend that you leave it alone. Only hollow out the SECOND CAT if you need to.
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Q. "The engine looks new and clean for a 73,000miles car so I was wandering is this not one of those the engine has been worked on and sent to Nigeria?"
"Since you said the engine is good when you had a look at it,will you recommend it for somebody? since every car has its own fault."
A. The Nissan 2.5L I4 engine is a very good and solid engine design. The basic engine is very reliable, the only problem was this exhaust systen flaw that was messing up some of the engines, and the root cause of the whole thing is that the computer was allowing a slightly too rich mixture in the exhaust, which in turn causes the deterioration of the pre cat. The real solution is to have the computer memory "reflashed" or "upgraded" to eliminate the root cause of the problem. But on a used car, it is also good to hollow out the pre cat because it is likely that damage to the pre cat is already being done, and that damage to the engine is likely to follow, if something is not done about it.
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Q. "One sunday morning,about 2 months ago, I started the Car and after some seconds i heard a sound like something has dislodged inside the bonnet and i thought it was the cat since I have read several reviews of it coming off and damaging the engine.I was already looking foward to the engine dying but the noise stopped as if the stuff has dislodged and off we drove to church and till now nothing has happened.I change the oil every 3months with 4litres, and the filter every 6months and the oil level remains the same."
A. Over here we have "Hoods" instead of "Bonnets". You could have the second big problem that those engines have, the "Butterfly valve screws coming loose and getting sucked into the engine" I have not had this problem yet. When I had my daughters engine apart, the screws were still tight. These are also called "Power Valve" screws, they are located inside the INTAKE manifold. Two small screws hold each butterfly valve onto the shaft, there are 4 butterfly valves (one for each cylinder), total of 8 screws. There are know to come loose and fall out. when they do, they have no place to go but get sucked into the engine. Once in the engine, they bounce around inside the clyinder, and can cause much damage, or if you are lucky, maybe not to much. It is just a matter of how the screw happens to bounce around in the cylinder, before finally getting blown out past the exhaust valve. The bouncing screw can bend or break the spark plug, score the clyinder walls, crack the head, crack the piston, or crack or bend the valves or valve seats. To fix these, the intake manifold has to be removed, then the screws removed and then cemented tightly back in place or cement new screws back in place.
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Q. "I change the oil every 3months with 4litres, and the filter every 6months and the oil level remains the same."
A. I would suggest that you change the oil filter at each oil change. How often you change oil depends on the miles, type of driving, and road conditions. Idling is harder on the engine, as well as dusty roads. Our Altima is driven in mixed City and Highway on clean roads, so I change oil and filter every 5,000 miles, using high quality Mobil One Synthetic Motor oil 10W-30 and a Purolator "Pure One" synthetic motor oil filter. 5,000 miles works out to be about every 4 months for us. It gets a new air filter every 15,000 miles and an Automatic Transmission Fluid Flush every 60,000 miles.
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Q. "Is there a way of knowing if the pre cat has been removed? Do they remove it before sending the cars to Nigeria?"
A. The only way to know for sure is to pull the exhaust pipe loose from the bottom of the exhaust manifold and look up inside and see if it is there. It is most likely that yours would still be there.
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Q. "When I bought the car, the service engine light was on and I complained because of the reviews I read on the net about it.Later since it was not giving any problems and many cars down here show that, I ignored it.I changed the oil and filter, it still remained but after taking it out on a journey of about 500km I noticed the SES light has gone off.It remained off until about 3 mths later when it came on.I always turn the fuel cap several times after refuelling.I serviced it again ie changed the oil,the light remained.Now I travelled again about the same distance as the previous one and noticed that the SES light has gone off again(2weeks ago), and has remained off till now.My question now is can one use the light to gauge when to change the oil?"
A. The check the SES Light, you need to read the codes with a Code Reader or Scanner, or have them by someone. Once you know what the code is, you use logical thought and mechanical skill to determine what the problem is and how to repair it. There are a lot of codes and it must be diagnoised properly.
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God Bless
E.D. in Sunny Florida, USA
Q. "You know this car so much that If I were in your position, I will erk out some living from it."
A. I don't need anything from this car. I have a good job at an engineering firm. I Only got so involved with this one because it is my daughters car, so I do all that I can to help her. I have worked on cars all my life, I've always been a car buff and motorcyle buff. I have worked as a professional mechanic in my younger days, but I retired from that. I still do all my own work on all my cars because I don't trust others, I do better work than them, I know exactly what is done and document all my work with paperwork and photos. My reward comes from having very reliable vehicles to drive (I have 3) and helping others, like you.
God Bless,
E.D. in Sunny Florida, USA
One more clarification,the car drives rough especially especially the owners side when it enters pot hole.It also shifts as if its gonna stumble when it enters pot hole.Is this a stabilizing rod or shock absorber problem? as i am already planning on getting one for a change.
I will keep the pics and show my mechanic what to do as i dont want him to mess up the stuff.
Thanks once more.
Chuma.
When the car is started, the fans does not come on until the temp is in the middle of the temp gauge, are all these normal because my Maxima and Blue bird's fan blows all the time.
Chuma.
When the car is started, the fans does not come on until the temp is in the middle of the temp gauge, are all these normal because my Maxima and Blue bird's fan blows all the time."
See my messege #154 in this forum, I explain the operation of the fans. The fans come on when the coolant temperature reaches about 202 to 203 degrees F, and the fans turn off when the coolant temperature falls to about 188 degrees F.
Good Luck
E.D. ISF
Chuma.
E.D. ISF
I thank God I discovered this site now I know much better, though ignorance is bliss.Can the scanners discover reason for low MPG? I am presently getting 18-22.3 in city and 26-31 in free way depending on driving conditions.I have read reviews of people getting 26/35-40 city/freeway and I get jealous especially with Camry and Honda.What am I doing wrong or is it the car?
Chuma, Nigeria.
Some of the top ones are:
Autoxray
Autotap
Autoenginuity
Mine is a 2001 model by Autoxray, it was $200 then.
They now run about $200 and up. They have handheld models, and also have ones that plug into a laptop computer to give all types of fancy displays.
Research them on the net , and you will find out all about them.
Also Goggle "OBD II trouble codes" and you will find out all about the trouble codes (Diagnostic Trouble Codes) and how to read and interpret them. The codes do not tell you what part is bad or what part to replace, they point you in the right direction in your search for the problem.
About your gas mileage, that is a matter of keeping the engine in good tune, to be sure all cylinders are firing properly, to be sure the transmision shifts properly, The transmission torque converter should lock up at cruising speeds, and driving habits play a big part, easy on the gas, keep rpms low when accelerating, and easy on the brakes. If you apply the brakes hard or stop fast, that is moving energy that is lost or wasted (lost gas mileage).
Good Luck,
E.D. ISF
Seems like your the one to ask around here so here goes:
I have a 2.5S with ~90000 miles on it. It burns 1 quart of oil every 50 miles. It doesn't appear that any coolant is getting inside the cylinders and the coolant level stays the same. I took out the spark plugs and in cylinders 2,3,4 you can see deposits and oil on top of the piston. The spark plugs look bad but nothing excessively bad. The car runs perfectly fine and there doesn't seem to be a loss of power. There is blue-ish smoke coming from exhaust as well. The problem started on the trip from FL to MD when the car was heavily loaded. Needless to say, I had to put in about 20+ quarts of oil just to get the thing home (it made it and still runs ok). I have had cylinder misfires. The oil looks really black (and not milky). I did a compression test and all four cylinders read in the 160-165 psi range.
I was thinking scored walls but compression seems ok to me (atleast not bad enough that it burns 1 qt every 50 miles) and the car runs fine with no loss of power. Next, I was hoping it was only a head gasket but no coolant is getting in the engine (not sure if it is possible for a blown head gasket to leak just oil into the cylinders). So now I'm hoping for bad valves (but seems weird that 3 cylinders would go at one time). I've heard things about the pcv valve going bad but could this be a cause as well?
Anyway, I was looking for your thoughts. If it is the valves, can they be replaced without having to take off the timing chain and cylinder head?
Thanks for your help!
Ben
First, I would check the PCV valve and hose, as a bad PCV can suck oil out of the engine crankcase and into the cylinders. You can temporarily disconnect the PCV and plug the openings and see if that makes any difference after 50 to 100 miles. Also, when the PCV is diconnected, see if you get much smoke (blowby gas) coming out of the hose that connects the PCV to the valve cover.
You said the oil was very dark, how long does it take to get dark after an oil change? How often do you change your oil? You may need to change your oil more often, but I guess by adding so much oil, it's like a constant oil change.
Second, the oil can get into the cylinders past worn oil control rings, those are the lower rings on the piston, each piston has 3 rings, from top to bottom, an upper compression ring, a lower compression ring, and an oil control ring. If the oil control rings do not work properly because they get broken, weak or damaged, they will allow oil to leak up past the piston into the combustion chamber and burn with the gas on top of the piston. Since your compression readings seem fairly ok, the walls are likely not scored. Replacing rings ia a major overhaul, having to remove the engine, very costly.
Third, another thing that can cause high oil consumption is oil leaking past the valve guides, but as much oil as you have to add, it would have to be more than just the valve guides.
If you need valve work, the entire head has to be removed and the head rebuilt at a machine shop. Have the engine and head checked by a competent machine shop. If you search these messeges you will find that I have went over all of that before and I have posted links to photos of the complete teardown and rebuild of the engine head removal, and head replacement, with links to many photos of it all.
Forth, another thing that could cause this issue is that the "Power Valve Screws" have a nasty habit of coming loose on these cars and they get sucked into the intake of the engine, and can cause severe damage to the engine, if they happen to take a bad "bounce" before they finally find their way out the exhaust. They can even cause a cracked piston, head or valve. See previous messages about this issue, or Google it.
Have you had any problems with the catalytic converters yet? Since you are burning oil, that oil goes through the cats and will cause them to fail eventually.
I would start first with the simplest thing to check, the PCV valve and hose.
Good Luck,
E.D. ISF
I checked all the spark plugs and they looked ok. Dirty but not excessively dirty. As for the oil, I change it religously every 3000-3500 miles. I have not done an oil change since the problem (figuring I was basically doing one all the time). Before the significant increase in oil consumption it didn't get black right away and the engine probably burned 1 qt every 1000-1500 miles. And then all of the sudden it shot up to 1 qt every 50 miles on the trip home. Now the oil is constantly dark even after adding more. When I pour in oil, there seems to be fumes coming out of the oil port in the valve cover. Not sure if this is because everything is hot, or if this is normal, or if it is exhaust fumes exiting from a busted valve that is being trapped in the valve cover.
From my understanding of what you wrote, it is possible to have a bad oil control ring but still have decent compression. Is this correct and do the rings usually fail all at the same time or could just one fail?
I have not had problems with the precat or cat yet. However there are codes that are stored and I will be borrowing a friends code reader tonight to see what they are. Since I had to add so much oil, I am already planning on having to replace the cat and the precat (but either hollowed out or with a header) assuming the engine can be fixed for a reasonable amount of money.
I guess my plan of action now is to check the codes and see what they say first. I will try to replace the PCV valve and hope that fixes everything. Then I would like to take off the exhaust manifold/precat and see what the inside of that looks like. If theres nothing left, I would expect the problems to be much worse than feared. I was also going to take off the valve cover and look around, but will I really see anything from just doing this? Next, I was going to check out the intake manifold and see if all the butterfly screws are still there (I am assuming thats the same thing as the "power valve screws").
Do that seem like a reasonable path to take?
One last question, is there any reason to take it to the dealership do you think? The car and exhaust components are out of warranty (~90000 miles) and since I have a code reader and already did the compression test, I don't want to pay for someone to tell me something I already know. I am figuring that since I don't have oil reciepts, a maintanence history through Nissan (I do everything myself), and the car is out of warranty, I will have no chance at getting Nissan to help fix/pay for anything.
Thanks again,
Ben
Thanks for all the contribution so far, its been wonderful joining this forum.I have indeed learnt a lot from you guys.
My exhaust pot has two outlets and I normally check the gas coming out of it.I noticed that the pipe to the right from the back blows out cold air while the one to the left blows out hot air.Is this normal? just a chance discovery by putting my hand there when i start it in the mornings.
I also want to find out the meaning of PCV valve and hose and where they are situated in the engine.I am a doctor and the PCV I am used to is 'Packed Cell Volume'.
Now I know better I am afraid to travel with this car, Ignorance they say is bliss, but knowledge is still supreme so I want to learn more and more.
Thanks to electricdesign (trying to figure out the name or guy name).
Thanks, Chuma.
But first, do what I asked in the previous message, check the engine crankcase for combustion blow by gases. Leave the oil filler cap ON the valve cover, pull the hose off the PCV valve. The other end of that hose should be connected to the valve cover. Start and run the engine and see if smoke or gas blows out the hose and if any, how much. A good engine will not blow any smoke, a bad engine with blow by will blow smoke. The gas or smoke is combustion gas that leaks past the rings into the cylinders. If no blow by, you still have a problem yet, since you know that the engine is consuming oil and that smoke comes out the exhaust.
It is possible that oil could be leaking past the valves, but it is hard to believe that that much oil could leak past them.
To look at the Pre Cat (first cat), don't unbolt the exhaust manifold from the engine. Unbolt the exhaust pipe from the bottom of the exhaust manifold (two bolts with springs), under the car, and look up inside the exhaust manifold. You will be able to see the lower cat screen if it is there. If the cat has blow out clean, that is one less thing to worry about, except for where the stuff went down the pipe (usually clogs up the 2nd cat). Unbolt the exhaust pipe to check the 2nd cat.
About the dealer, I don't think you will get any help there, unless you like to spend a lot of money.
Good Luck,
E.D. ISF
I have been looking at mine with my mechanic and wondering where to approach it from.He wants the approach you advised against so I need reasons to give him.
thanks,remember question 301 please.
Chuma.
So after all that, I decided to recheck the compression since nothing seems to be adding up to why its burning so much oil. Well low and behold the compression was 135-142 psi for all the cylinders. I don't know what I did differently the first time to get much higher readings. I haven't really driven the car since the last test. If anything, this time the engine was hotter so you would think higher compression numbers. So its looking much more like a new engine will be needed. And if this is the case I will probably be getting rid of the car unfortunately. I love the car when the engine is working. I think getting a new engine or having the dealer replace it is just not worth the time/money, especially when the cars only worth ~$5700.
Thanks for your help ED!
Ben
About the exhaust at the back of the car, you have a single exhaust with a single muffler with a single tailpipe that splits into two tailpipe tips. As long as you have good exhaust gas flow out of either pipe at the back of the car, you are ok. This is only for single exhaust cars. Cars that have dual exhaust, such as the V6, must have good exhaust gas flow out of BOTH left and right tailpipes.
About the "PCV I am used to is 'Packed Cell Volume'." PCV Referring to automotive is Postive Crankcase Ventilation.
"electricdesign (trying to figure out the name or guy name)." That is simply my job as an electrical designer, hence the abbreviation E.D.
Good Luck,
E.D.
Check you compression tester, it's always best to use quality reliable equipment, because wrongs readings can throw you way off track. I use a qualitiy screw in Pearless compression tester, with a heavy duty 2 foot flexible hose.
"So its looking much more like a new engine will be needed." Unfortunately, I think you are about right, since the compressions are now reading low. That would give much stronger indication that oil is leaking up past the pistons and rings into the combustion chamber and burning with the oil.
I would agree that a $5700 car is not worth a new engine, unless it is a restoration project or of great sentimental value.
Good Luck,
E.D. ISF
Maybe I will use his tools and pit in the workshop and have a look for possible hollowing of the pre cat and have peace.
The PCV's air flow is supposed to be clear and colourless I presume.The one in my Bluebird brings out dirty oily black gas but I cant seem to locate that of my Altima.
Thanks, Chuma.
Since you may try to look into the exhaust manifold/pre cat yourself, look at what I wrote in messege #306:
"The bottom bolts of the exhaust manifold, where the exhaust pipe connects, definitely do get rusty and stuck tight. That work is easy for me because I just use my acetylene torch to heat them red hot and they come right off."
I would count on the bolts being rusty and tight, so try to be prepared for the worst. Exhaust components usually are rusty and stuck, so this should not be a problem if the mechanic is familiar with this type of work. I don't know if you have an acetylene torch or anything to get rusted tight nuts loose. If you get stuck, and can't get it off, then just let the mechanic have a crack at it, as he has to take that exhaust pipe loose anyway, before he can remove the exhaust manifold. See teardown photos DSC06886 through 06888. If you try to hollow out the pre cat, I would recommend that you first remove the oxygen sensors to avoid damaging them. You may likely need a special socket for this, if they are tight, and they usually are. The special socket has a slot up the side to allow the socket to slip over the wiring. See teardown photo #06892, this photo is on the upper O2 sensor for clarity of the photo, but you need to remove the lower O2 sensor also, as it is in the most danger of being damaged during the hollowing out process.
The PCV valve is located bolted with 2 bolts to the Intake Plenium, on the end of the hose from the valve cover, see teardown photo # DSC06959. If you pull the hose off the PCV and start the engine, there should be only a small amount of gas, if any, coming out of the hose (coming out of the inside of the engine), and it should be colorless (we have color here, not colour). If dark or smokey, it indicates an engine problem, which is too much combustion gas in the crankcase, also called blow by. The cure for blow by is a new or rebuilt engine.
Good Luck,
E.D. ISF
Unscrew O2 sensors carefully, if they start to get tight when unscrewing them, spray some penetrating oil on the exposed threads and screw it back in a little and work the sensor back and forth a few times to work the oil into the threads. Apply oil as often as needed. It should loosen and eventually come out. Before putting a used or new O2 sensor back in, coat the threads with a small amount of Neverseize compound (available at auto parts stores). Put the Neverseize carefully only on the threads, do not contaminate the sensor with the compound. This will help in the future, in case you should have to remove it again.
Good Luck,
E.D. ISF
The PCV valve is hidden under a plastic covering of the engine (there is this black plastic covering the top of the engine with 2.5 written on it that covers the engine I didn't see it in yours). If I remove it I believe I will be able to see the valve and some other things like the plug.My car is even the same color as your daughter's - Gold.
I have looked at the pics as you directed and all were clear.The oxygen sensor, I am really amazed because down here the wires are cut by the mechanics with the belief that it does nothing.My 1988 nissan bluebird even has one but the wires are cut for a long time now and i learnt that when bad will contribute to increase fuel consumption -- is this true?
How is your daughter's Altima performing? we need a feedback from you for that heroic performance (to think you did the overhauling of that engine all alone). This will aid me so as to know when to sell the car off, its just 7 months old with me now.I don't need a liability now especially with the crashing prices though its still expensive down here, I bought mine 1.7million Naira which is about $14,780 including shipping and clearance at the wharf down here.You guys are lucky there, the cars are cheap there.
Thanks, Chuma.
Oxygen Sensor, don't cut the wires! You need the O2 sensor working, because that is the main component that the computer uses to regulate the amount of fuel injected into the cylinders. The signals to the fuel injector are called "Pulse Width Modulated" signals. That means a pulse of voltage is sent to each fuel injector, a short pulse opens the fuel injector to only open for a short time, allowing only a small amount of fuel to enter the cylinder. A longer pulse allows more fuel to enter. The computer varies the lengths of the pulse according to the output of the oxygen sensor. If the O2 sensor reads rich, the computer tells the fuel injectors to go lean, If the O2 sensor reads lean, the computer tells the fuel injectors to go rich. It is always in a varying state, according to the reading of the O2 sensor. Now if you cut the wires, that will put the computer in the "default" state or "Open Loop" state, which just runs on a set of predetermined values that are not fuel efficient. Fuel consumption will increase, the engine will use more gas and not run as clean. Try to maintain the computer system and sensors. If you can't, then do the best that you can. You must have internet access to get to this forum, so try using Google to find the information that I previously told you about, it will explain all that I have said and much more.
My Daughters 2002 Altima 2.5S is performing very well. I did a Sevice, oil change & filter change last weekend. It is using about 1 quart of motor oil in about 2,400 miles, which is OK. I change the oil and filter every 5,000 miles, using only Mobil One 10W-30 Synthetic Motor oil and Purolator Pure One Synthetic oil filter. I was noticing some vibration on the serpentine belt, I may have to change the belt tensioner soon. Other than needing some new tires, it is doing great.
Thanks for the vote of confidence, but not needed, as I said before, I have done this type of work all my life, rebuilt many engines and transmissions. I retired from that work, but I still do it if needed, and my daugther really needed the help, so Dad had to help her out.
I hope most of your questions are answered now.
Good Luck
E.D. ISF
However, mine only misfires upon start up and shortly after. Never while driving. Swapped coils and checked plugs and still misfired #3. Oh, it also idles slightly higher...at almost 1500 sometimes, but doesnn't surge.
I'm thinking maybe the #3 injector is not closing completely at idle or upon engine shutdown....thus loading up the cylinder with fuel. Sound possible???
Thanks for any info you may have,
Rick
One thing to check first - Do you loose any coolant from the radiator coolant tank, or do you have to add any coolant, and if so, how much and how often? The symptom sounds like a small amount of coolant leaks into the cylinder when the engine is shut off. Later when the engine is cooled down and restarted, the small amount of coolant in the cylinder causes the spark plug to missfire for a minute or less, until the coolant is all blown out, then the engine runs normally.
The high idle may be related to the above or not. Check the PCV valve and check for vacuum leaks. Look for unplugged, loose, or cracked vacuum hoses. Check to be sure the upper and lower intake manifold bolts are all tight. Check to be sure the the O-Rings at each injector is not leaking or sucking air. Squirt oil on these things and listen to see if the speed of the engine changes. Connect a vacuum gauge to the intake plenum and see if the vacuum is good and steady.
Fuel injector #3 might be the problem, but not as likely. Do you use a fuel system cleaner or additive? You should add a fuel cleaner additive to the gas tank at least every oil change, to keep the injectors clean. If you have not added any, try adding some and give it time to work. Use an STP type or Seafoam.
Another problem that may cause the high idle could be the throttle body, Try carefully cleaning it with throttle body cleaner. Be sure the air filter is clean and that the air intake tube is not cracked or leaking anywhere. Sometimes, the Mass Airflow sensor needs to be cleaned, but they don't usually give problems on these vehicles, unless they are allowed to get dirty.
Good Luck,
E.D. ISF
The serpentine belt you mentioned just made me remember something.Is it the same thing as the fan belt? and what is the tensioner? The belt in my Altima (right side of the engine) wobbles and it appears its the lowest pulley holding the belt that does that and causes some vibration when I put on the A/C.
I think I need some help with regards to this.Does the pulley get damaged and does the wobbling affect the function?
Thanks, Chuma.
Good Luck,
E.D. ISF
'GROOVED pulleys are on the INSIDE of the belt loop, and SMOOTH pulleys are on the OUTSIDE of the belt loop'.
This is not clear to me.Which one is the autotensioner? Is it the pulley above and just behind the compressor pulley? Thats the one that wobbles a bit when the engine is idling.The compressor pulley is grooved while the one I am referring to, next to it is smooth and on the outside(just went to examine them). Is this the meaning of the statement above? that is the grooved pulleys get the rough part of the belt while the smooth ones get the smooth part of the belt which is on the outside.
Thanks, Chuma.
Is the autotensioner one of the smooth pulleys
Smooth pullys are outside the belt loop, the back of the belt rides on the smooth pullys.
The pully that you see bouncing (not wobbling), is the autotensioner.
Good Luck,
E.D. ISF
Thanks, Chuma.