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Nissan Altima Engine Failures

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  • I had GAP insurance...I had an extended Service Warranty..and of course, Full Coverage insurance. The bad part, is my sister and her boyfriend was taking his daughter back to her mother's house. And all the girl's christmas was in the trunk of the car, everything was destroyed. My insurance company will pay the value of the car...and Gap will cover the rest...but what about all my personal items in the car..and the little girl, what about her christmas that was in the trunk...my insurance company doesn't cover that. It's been a bad ordeal all the way around. I believe Nissan should be responsible for SOMETHING..it's very disappointing to say the least..
  • jd10013jd10013 Posts: 779
    How could it be the owner's fault, do you think? I"m trying to come up with something. I guess they could have set it on fire on purpose

    I knew a guy when I was in HS who decided to replace his fuel filter, but failed to tighten everything. the leaking gas caught fire and totaled his car.

    there are lots of ways a car can catch fire other than a defective car.
  • jd10013jd10013 Posts: 779
    depending on the amount of damage, it could be impossible to determine the cause. To me, it sounds more like a freak accident than anything else.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 45,641
    But this is a NEW car. I would think Nissan would be freaking out about this.

    I think the owner needs to send a letter to the Zone Office and use strong but respectful language as to what happened. The dealer won't care about this, just by-pass him.

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  • jd10013jd10013 Posts: 779
    considering the volume of altima's sold, I can't imagine them freaking out over one catching fire. especially considering that there are numerous ways for a car to catch fire that don't involve manufacturing defects

    as I said in my previous post, sounds more like a freak accident/occurrence than anything else.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 45,641
    Well the original post says that he reported the car smoking to the dealer prior to the fire and he apparently has record of this. One would not be unreasonable to suggest that 2+2=4 in this case, although proving it might be difficult.

    Perhaps settling it all by insurance is the best way but it is my understanding that all engine fires are taken quite seriously by manufacturers.

    I know when I worked for Benz this got our attention right away.

    Of course, this Nissan was a 2007, so that perhaps does muddy the waters considerably, that's true.

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  • kcvabkcvab Posts: 3
    I met a mechanic today who fixed 2 Nissan Altima for the same problem: loss of power and high oil consumption. All he did was hollow out the main cat converter.
    He showed me the honeycomb chunks that were filthy on one side and clean on the back side. He explained that the exhaust was being backed up with pressure causing the oil to spew out of the engine. That explained each time opened the hood I saw oil everywhere.
    I was consuming 4 qts of oil every 220 miles. I'm lookng forward to see what my oil consumption is now. Note that hollowing out the main cat will cause the SES light to stay on. I understand that $5 O2 sensor should take care of that, but that is the least of my worries now.
    Just thought I would share my story. Good Luck!
  • Interesting solution. The advantage to that is you don't have to worry about it going bad again...
  • that is a pretty clever solution. 4 qts every 220 miles? is that on a V6 or V4? what year?
  • To all those who have posted latey in this forum, I suggest to anyone who has an Altima 2.5 to be sure to read ALL the messeges in this forum starting from #1 to the very end, they are all important. My first messege in this forum was #75. Please tell anyone you know that has an Altima 2,5 about this forum, and warn them of the possible problems that they may face. It is MUCH better to address this problem, BEFORE you need to buy a new engine.

    Please read message #357, or go to or click on the link below:

    electricdesign, "Nissan Altima Engine Failures" #357, 31 Jan 2009 11:31 am

    Then read all the rest of the messages. It will open your eyes.

    Good Luck,
    E.D. in Sunny Florida
  • I own a 1995 Nissan Altima ans just about a week ago my cruise control went out. The cruise control light, I noticed, was flickering for a few months and now it doesn't work at all. Could it be my fuse.
  • rondholrondhol Posts: 32
    I had replaced the head gasket 10k miles/1 year ago. My 2002 altima 2.5 consumes 0.5 quarts per 1k miles since my last oil change (5k miles interval) with Super Tech full synthetic, Florida weather. The pre-cat was new just before I noticed oil consumption. Now runing 10w-30 Synpower and the the engine run smoother but still consumes oil at the same rate and even more at highway speed (60mph). I don't feel any power loss and can speed up to 100+ mph and 5k rpm on neutral.

    I want to keep this car for a while since I already dumped $3k for all the repair: 3 New engine mounts, struts, head gaskets, brakes. Will the car run for another 50k miles? What is your suggestion Electricdesign?
  • Hmmmmmmm........well that puts me on the spot, as I can't predict the future, and these Altimas seem to be unpredictable. Some seem to run with little or no problems and others have a host of problems. I have used both the Mobil One and the Syn Power synthethic oils, both do very well. I never tried Super Tech oil. How many miles on the car, and how many miles on the CAT? The best I can say is to keep up all the normal maintenance, and keep a close eye on the oil. Do you have any oil leaks from the engine? You also need to check to see if your engine oil is getting sucked through the PCV valve. If you have serious concerns, you can test, or have tested, the engine cylinders compressions to determine the general health of the engine. Never let the engine overheat, as that will kill it faster than anything. Your engine may last another 50K if you keep a close eye on it and maintain it well.
    Good luck,
    E.D.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 45,641
    1 quart per 2,000 miles is nothing to worry about as long as that remains constant. There's hardly a Subaru 2.5L engine on the road, for instance, that doesn't do that.

    It's when you start to use oil, and you notice that this consumption steadily declines, and then starts to hover around a quart every 1,000, that you need to be concerned IMO.

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  • rondholrondhol Posts: 32
    Thanks for the input for 75k miles engine (have it since 65k miles). The pre-Cat is installed 7k miles ago, I don't see any trace of oil in the engine except very thin oil film on the valve cover gasket after a long trip. The inner side of PCV valve hose is dry.

    I will check my car regularly. Swooshing noise caused by air pocket was fixed after changing the swelling radiator cap. With a long wheel base, the ground clearance of this Altima is too low . Sometimes the bottom of the car touch the large bump when 3 people on the back seat.

    I will post the update of the next oil change (Mobil 1 0w-40/ GC 0w-30).
  • Following-up with post 370. THANKS BE TO GOD. He deserves the glory. I prayed and God answered. With the 2007 altima transmission, they replaced it with NO CHARGE. They did not openly tell me that it was a manufactured defect. However, I agreed to pay half the cost because I needed my car fixed. After speaking with consumer care which denied the claim, I spoke personally with the service manager at the dealership. He contacted the regional manager which only agreed to pay half the cost. Another regional manger was assigned to this dealership and the new regional manager agreed to cover the cost - "NO CHARGE".

    I must say the service manager at the dealership willingly worked with me and tried to ensure I get what was right and fair. This was my 3rd nissan. So therefore, to keep me as a customer, they agreed to cover the cost. I thank God for the new regional manager and the service manager. By the way, customer care did not contact me after numerous attempts to request for another review of my case.

    I still believe that Nissan need to do a better job of reviewing cases and hearing customers when problems are discovered with their vehicles. They were known for longevity and quality. Both of these areas are no longer a factor in producing a dependable vehicle. Hopefully, if they are reading forums such as this, they may see the errors and become the great manufacturer that they once were years ago.
  • altilove89altilove89 Posts: 6
    New to the forum. I recently purchased a 2003 Nissan Altima 2.5 S fore $8000 down here in Orlando. Car has been running really great but it had problems and after reading this forum I have a lot of the same problems you guys do.

    The car burnt through 4 quarts of oil after about 2000 miles (7 weeks) and was puffing blue smoke out the exhaust when I would start the car. I took my car to a local nissan dealership today and found out my car's cat is covered for 80000 miles (my car has 61000)

    A mechanic who overheard my conversation with the service manager said asked me "Does you car puff blue smoke when you start?" And when I said yeah he explained that I needed a new engine. All the problems you people have had, but I got luck to still be covered by that 80000 mile warranty and I will not have to pay $6500 in repairs) :sick:

    I plan to keep the car as I have only had it for two months (and I owe probably 95% of what I paid) Plus I love third and fourth gen Altimas. This is also my first car (Im 19)

    Once the new cat is put in I'd like to have it hollowed out so this problem doesnt happen again. If ED stil lposts I'd like to know what he thinks.

    Third gen altimas might be crap but I still love them ;)
  • rondholrondhol Posts: 32
    QR25DE is not bad engine. Without pre-cat it will last hundred thousands of miles as other Nissan engines. My oil consumption is less than 1 quart per 3k miles with Synpower 10w-30. Small oil consumption is normal if you have short trips <9 miles per trip caused by fuel dilution. My Used Oil Analysis is pretty good with 5k miles even with fuel dilution.
  • jd10013jd10013 Posts: 779
    QR25DE is not bad engine. Without pre-cat it will last hundred thousands of miles as other Nissan engines.

    even with the pre-cat it will probably last hundreds of thousands of miles. if you compare the number of QR25DE engines sold to the number having problems and your odds are pretty good. on top of that, its mostly limited to the 2002 model (first use of QR25DE) year. once the problem surfaced, it was corrected and a recall issued for the effected vehicles. there was probably some carry over into the 2003 model, but anybody owning a mid to late 2003 and up really has nothing to worry about.

    the problem was never with the engine, and not really with the pre-cat either. it was primarily with the fuel mixture, or more precicesly, the programing of the ecu that controlled it.

    I'll share a story with you from a couple weeks ago. First off, I work for a company that provides products and service to business. about 65% of our customers are automotive repair shops and dealerships. A couple weeks ago I was in one and talking with the owner. I couldn't help but notice he was working on a 3rd gen altima. I asked him what was wrong with it, and he said he wasn't sure, but that it needed a new engine. It was burning massive amounts of oil. He hadn't finished checking it, but had seen enough to know it couldn't be fixed. Anyhow, I told him about the pre-cat and oil consumption problems, and suggested he look at the pre cat when he removed the engine. To make a long story short, when I was back in his shop a week later I asked him if he had looked at the pre-cat and if it was all broken up.

    He said no, it was in pretty good shape. normal for the 80k miles that were on it.

    Now I'm not saying the pre-cat problem isn't real, or that it doesn't happen. But there are a lot of things that can damage an engine and cause it to burn oil. Primarily taking care of it. and when your dealing with (as many people here are) used cars, you don't know if it was taken care of, or even how hard it was driven by the original owner. Heck, you don't even know if the recall to correct this issue was performed.
  • altilove89altilove89 Posts: 6
    My car according to carfax was manufactured in july 2003 so its a later 2003 model, still had the problem.

    just got the engine fully replaced 2 days ago at 61000 miles along with the pre cat

    car drives beautifully now, still plan to have the pre cat hollowed out, i dont want to take any chances on this thing happening another 61k down the road. a car should not need a 3rd motor at 122k miles, nonetheless even a 2nd one at that many miles

    me being 19 however and wanting my first car right away i didnt even do the carfax report before i bought my 2003 altima 2.5 s

    i had actually done the report a few weeks ago and found out my car was once a rental car back when it was brand new :mad:

    mechanically speaking even before the engine was replaced the car seemed fine and drove fine

    i will need an alignment sometime in the future but it is not a major issue at the moment. i also may need to change the timing belt

    since ive had my new engine though i hear a weird noise that sounds like water rushing through some kind of pipe when i start the car, and also when i accelerate. does anybody know what that might be all about? :confuse:
  • rondholrondhol Posts: 32
    That swooshing noise is dangerous if you don't fix it ASAP. It may cause head gasket failure($1200 repair). It is easy, Park the car uphill (radiator at the higher level). When engine is COOL, Open the radiator cap (check the condition, you may need new radiator cap), Turn the heater and fan at max, Start the car and squeeze the coolant hoses to remove any the air pocket inside the coolant line. Top the coolant level up (both on the radiator and reservoir) and replace the radiator cap.

    I had that problem but it was fixed after do that steps and install new radiator cap from Autozone or dealer . My previous radiator cap was swelling caused by oil residue from the head gasket replacement.

    Your car has TIMING CHAIN (no need to be replaced until 300k miles), If the car go straight on the FLAT road and the tires have no unusual worn, you don't need alignment. You may need to replace the front struts, passenger side and rear side engine mounts if you race the car a lot and the brake pads at arround 80k miles city driving.
  • altilove89altilove89 Posts: 6
    that noise actually went away i no longer hear it, car pulls to the right ever so slightly on flat roads

    never race my car, i care about it too much to do something like that, i never go any faster then 70 mph anyways because my car would start to guzzle gas (my average mpg according to the trip comp is about 25.5 mpg)

    tires are ok, the right front tire is almost bald, the other 3 are very good, havent bought a tire due to serious lack of cash at the moment
  • rondholrondhol Posts: 32
    If your front tires are match (same brand and date installed) but only right side is worn, then you need alignment. Change the tires in pairs 2 or 4 at once. The pulls to the right effect caused by lower (worn out) right tire. You can buy good brand (Micheline, Good year, etc, NOT CHINA tires) used tires in pair for less than $35 each. but read this first: http://www.carbibles.com/tire_bible.html

    By the way, check your radiator cap , coolant level (both on radiator and reservoir), and the hoses after the engine is cold (if it is collapsed).
  • keilsekeilse Posts: 16
    Hi! I have a 2002 3.5 liter Altima and the problem with the cats is prevalent throughout my ownership of the vehicle. I have had 5 cats replaced, and the last time, Nissan forgot to put oil in my car and I battled with them for a year, and they replaced the engine and cats with all new Nissan factory parts. Well, the new engine has less than 10,000 miles on it, and the cats started coming apart internally just like always. I had a mechanic friend hollow out all the cats and in the process of doing so, we noticed the resonator pipe had a big crack in it, which no doubt was leaking exhaust. He removed the resonator completely, hollowed out that cat, and then welded a new pipe in place of the resonator piece. The other two cats up in the front of the car were also hollowed out. The very front one, the hardest to get to, closest to the heat shield was virtually impossible to hollow out. The core if the catalytic had hardened into a solid mass, and there was absolutely NO AIR able to get through it. The mechanic couldn't hammer it, drill it, use a saws-all on it - NOTHING was going to break it up to remove it. So my friend cut open the cat in the middle, and grinded the catalytic core material out of it, and then welded it closed and put the pipe back on. Now, the SVC engine lite (obviously) has come on, and the exhaust leaks right into the cabin of my car and it's unbearable. I don't know if there is a leak at the weld spot from my friend or what, but I need to know what to do to make this car run right and not asphyxiate me in the process. Replace the left bank cat and leave all others hollow and then tweak the 02 sensor? Please advise if you are able! I really appreciate it very much!!

    Sincerely,
    Sara Keil
    keilse01@verizon.net
  • rondholrondhol Posts: 32
    first of all, Don't bring your 02 to that Dealer again.

    3.5L VQ engines rarely have pre-cat problem. Since you have new engine and cat, may be the culprits are MAF sensor, ECU update, or EGR system. If it runs too lean/rich, your engine and cat will be bad faster. Check the sparkplugs to confirm rich/lean mixtures. Buy header instead of breaking your head finding the leak.
  • Definitely try to find another Nissan dealer, better yet look up reviews on local nissan dealers and see who has the best overall reviews and choose the dealership with the best rep.

    The 3.5 SE v6 engine is a much better build then the 2.5 S, i actually wish i had spend the extra $1100 for the 04 altima with the v6 engine then the 03 2.5 S.

    Im suprised that the V6 has this problem as well, considering most V6 altimas are virtually problem free.

    My advice to anybody buying a Nissan Altima made between 2002 and now, spend the extra money and sacrifice the gas mileage for the v6, you'll have much less issues then with the 2.5 v4.
  • keilsekeilse Posts: 16
    The 2002 3.5 is FAAAAR from problem free. Almost every single person that I have seen at the dealer, on the street, or in any forum has the same problem as me - the cats go bad, come apart internally, and the particles get sucked out the exhaust, or if not that, then you have NO POWER. The design of the entire exhaust and cats is BAD. Replacing the cats on any car more than once in a 100,000 miles is ridiculous.
  • keilsekeilse Posts: 16
    Get a lemon law lawyer and sue. If you bought it used - your screwed - but new - the law is that any car that has had the same problems 3 or more times in a row is a LEMON and the dealer can do one of the following based on whatever choice YOU make - 1. Give you a full refund for the car (original prchs price) as well as reimburse you for any and all expenses related to the repairs...including rental car bills. 2. Give you a new vehicle of equal value and reimburse you for the expenses related to repairs. I WISH I HAD DONE IT AT 40,000 miles. But the cats are warrantied for 80,000 miles so I went ahead and kept the car. I battled Nissan North America for a year and they finally gave me a brand new engine and cats plus reimbursed me for ALL my expenses related to only the catalytic problems and ALL the frigging rental cars which was over $8,000 in cash. They wanted me OUT OF THEIR FACE and once I threatened to sue them for about $80,000.00 they straight paid to have me be gone! Good luck to you!
  • brossrbrossr Posts: 2
    I have a 2002 Nissan Altima 2.5 S which I bought new. It has always has all recommended maintenance performed and all maintenance has been performed by the Nissan dealership. The other day the check service engine soon light came on soon after I started the car. A couple of times in the last few days I had noticed that when I first started the car in the mornings it ran i little rough (not much) for about 5 seconds immediately after starting but that was barely noticable and almost immediately stopped after which the engine ran perfectly. I decided to drop it by the dealership and have it serviced. The last maintenance (oil change) had been done about 3000 miles ago, so it was time for scheduled maintenance, so I was also having the oil changed and the tires rotated. After about an hour the service guy came out and told me that the code on the service engine soon was a "cylinder 2 misfire." He said my antifreeze was a little low and they were doing a compression test as it could be a head gasket problem. He said the slight roughness for a few seconds when the car was started in the mornings was probably because antifreeze had leaked into the cylinder and once it burned off (a couple of seconds) the roughness went away. Because it was going to take them a while to do the test I told them to just call me when the car was ready and I left and went on to work. Serveral hours later the service guy called and said it was a
    head gasket problem, but he really thought I needed a new engine ($5300). They had found a little coolant in the cylinder and he said my oil was 1/2 quart low and although the catalytic converter didn't show as bad, he was afraid that if I just had the head gasket replaced ($1800), the engine would still probably need to be replaced and the head gasket replacement would be for nothing. This car only has 66,300 miles on it, has always has all recommended maintenance performed by the dealership, and has never been driven "rough" as I am a very conservative driver. I have read about other problems with this engine and the catalytic converter (or pre converter) failing and resulting in engine damage requiring engine
    replacement. This has really bummed me out. I bought this car because I was told, and had read, much about Nissan's reputation for solid cars that ran a long time. Now, here I am with a car with only 66,300 miles (it should just be getting broken in good) and I'm being told that I should replace the engine. If a well-maintained, conservatively driven car has engine failure at 66,300 miles, that sure seems like a
    manufacturing defect to me. I have read that the catalytic converter is warrantied for 80K miles and if this is true, and it had anything to do with the engine problem, it seems to me that this engine should be replaced by Nissan, especially now that I have read that this is a somewhat common problem with the 2002 Altima engines.

    I picked the car up and told them I would have to decide what I wanted to do. He said when the light came back on to bring it back so they could see if it gave the same code and he wouldn't charge me for that diagnostic. He also told me to check the oil about every 3 days and if it went down, don't fill it but bring it to them and let them see how much oil was being used (oil comsumption test). It's been five days and no service engine soon light, the oil level is fine and the car runs fine; there is not even any roughness when I initially start the car in the mornings as I had noticed a couple of times previously.

    Does all of this sound right? I'm not sure what to do and the thought of having to spend over $5K on repairs has me sick.

    FYI, I went back and read all the posts on this forum and it seems as if some people have been able to get Nissan to cover the repairs and others have not. If I do have to pay for a new engine myself, would I be better off price wise trying to find a good independent mechanic to do it? If I have to pay for all of this myself, my faith in Nissan will be destroyed.
  • keilsekeilse Posts: 16
    Rough engine running is a symptom of a much larger issue...

    Why exactly did he say you need a new engine? You need a new head gasket - but why? What broke in your engine to cause the gasket to become fouled? These cars DON'T burn oil and have gaskets go bad out of the blue - and I would bet money that if you only replace the gasket - your engine will experience a catastrophic failure that can only be remedied with replacement - either of the car or the engine. I would also bet money that the gasket is f-ed up because catalytic converter material has gotten sucked back to the engine....this is an event known as "BLOW BY". (It is a physical impossibility for the 3.5 to experience blow by because of the 'Y' shaped exhaust...I called 4 Nissan dealers and asked and all of them said this.)

    I don't want to bum you out even more, but if I were you, especially given the info from Nissan, I would file suit under the lemon law (what state are you in?) and get a full refund for the car, because I can guarantee that these issues will continue. The only way that you can avoid these issues if you can't or don't want to get rid of the vehicle, would be to make some modifications to your vehicle yourself. There is a guy that has postings for the same vehicle as you that did this and I pasted his advice below...

    Well people, I think I have a handle on this oil consumption problem with the Nissan Altima 2.5S. Maybe not a solution, but at least a good understanding of what is happening and why. My daughter has a 2002 Nissan Altima 2.5S that she bought in December 2003 with 29,730 miles. It is starting to exhibit excessive oil burning at 97,000 miles. At the last oil change service, she came in with the engine oil very low, so low it would not even touch the end of the dipstick, the dipstick would pull out dry. I told her to check the oil frequently now, at least once every two weeks, and she now keeps a spare bottle of oil in the trunk. I have done all the service on this car since she has had it, so it has had excellent service. It always receives full synthetic motor oil and synthetic motor oil filter. We are monitoring it now to see what rate it is using the oil. There are no oil leaks at all, so it must be consuming the oil. I guessing right now about 1 quart in about a 1000 miles. I have a good idea of what could be causing this to happen because of several events that have happened.

    First, I heard and read about the TSB and Recall on SOME of the cars about the problem with the precatalytic converter. My daugher took her car to the dealer and asked if this precatalyst recalled applied to her car, They looked up the VIN, and of course they said no. My understanding is that "under certain conditions", material from within the precatalyst can get sucked back into the engine, and the small particles can damage the cylinders, rings and plugs while bouncing around in the engine. I always thought this was very odd, as exhaust gas is supposed to be coming OUT of the engine, and INTO the precatalyst, and then OUT the precatalyst and DOWN the exhaust pipe and OUT the tail pipe. SO, how could this material go back up into the engine when all this exhaust gas is supposed to be coming out? It would seem that there would have to be some kind of pressure or force from somewhere to push the material back through the engine exhaust ports into the engine, but from where? So I thought about this for a while, then my daughter calls and says her 2002 Alitima 2.5S is making this strange sound, like air whoosing, when she steps on the gas, and the engine had very little power. But she kept driving it for a while until she could get by my house for me to look at it. When I did look at it, it did indeed make a strange whoosing sound, like a sound of rushing air when I stepped on the gas, at idle it sounded almost normal. So I looked underneath the car and I found exhaust gas was gushing out of the point where the bottom of the exhaust manifold/precatalyst is connected to the exhaust pipe with 2 springs and a gasket. It makes kind of a flexible connection so the the engine can rock back and forth a little bit. So I said that there must be quite a bit of pressure in the exhaust pipe for it to be leaking out like that with such force. So then I went to the back of the car to see how much gas was coming out the tail pipe, and when I checked I could feel none! When she revved the engine, I could barley feel a bit of exhaust gas. The exhaust was plugged up! So I got underneath the car and found that the exhaust pipe continues under the center of the car until it gets to this 2nd Catalytic converter before the muffler, it looks like a double cone, narrow at each end and fat in the middle. I felt the temperature of the exhaust pipe, and it was hot near the exhaust manifold, but got cooler as I felt closer to the 2nd catalytic converter. 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. The gasket at the flexible connection was still perfectly good. The exhaust gas had been allowed to leak out at that point due to the spring connectors, when the pressure in the pipe got high enough the springs would compress, allowing the joint to open slightly, and allow the exhaust gas to leak out. Therefore, the pressure was high in the exhaust pipe all the way from the engine exhaust ports to the 2nd catalytic converter. This section of precatalyst/exhaust manifold and exhaust pipe has a volume and acts like a pressure tank holding high pressure when the engine is running, having higher pressure when the engine runs faster. So this is what happens, the exhaust coming out the engine exhaust ports is not a constant flow, as the exhaust valves are opening and closing very fast, so the gas comes out pulsating, pushing against the already high pressure in the precatalyst. At the end of a strong pulse, the high pressure in the precatalyst can actually push some gas back up into the exhaust port, because of the high gas pressure in the precatalyst. So, the Exhaust gas is exhausting into high pressure, and some of the high pressure can push back up into the exhaust ports in between the high pressure pulses of exhaust gas coming out of the exhaust ports. Under "certain conditions" it is possible for material to blow from the precatalyst back into the engine causing engine damage.

    Continued in the next posting....
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