# Yeah, another 02 Altima cat question



## vpanell (Sep 11, 2010)

:newbie:

Hi everyone. Thanks for this very informative forum. Doing a search I beleive the problem to be the same as alot of other Altima owners are having. 2002 Altima 2.5 with a possible clogged cat. 

I crawled under it to check out a very strange noise. Sounded like a turbo releiving pressure. When the engine is revved the expansion portion of the exhaust right before the converter under the car swells and then sounds like it is releasing pressure. (a novice description at best) I took it to a muffler shop and they said it was the converter on the exhaust manifold that was clogged. The upper cat does get very hot. He said the lower could just about be touched without burning yourself.

I thought it to be the lower cat with the way the expansion joint swelled like it was backing up.

As with alot of other folks on here the car has lots of miles. It makes a bit of a rattling noise when started (death rattle?) and consumes oil.

The upper cat is somewhat expensive. What can I expect from the engine? I know you cant say for sure but do you think it is worth the cost of replacing the cat?

Thanks again for this very informative sight. Glad I found it.

Vinni


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## smj999smj (Jan 1, 2006)

The upstream cat is obviously more likely to get clogged than the rear cat, as it will act like a filter for the exhaust prior to reaching the rear cat. If the engine is burning oil, this is likely the reason for the converter being clogged. Maintained Nissan engines in general were never known for having oil burning issues until the '02 Altima 2.5L arrived. First it was said it was due to the chrome rings used on the pistons not seating. Then, it was said that the pre-catalyst was breaking down and being sucked into the engine via the exhaust valve and subsequently scratching the cylinder walls (this engine does not have an EGR valve, rather uses the variable camshaft timing to allow exhaust to be sucked into the cylinder via valvetrain timing). A recall was put into affect and many improvements were made and many short blocks replaced due to oil consumption. I'm sure there are a few out there that either didn't have the recall or had it and have started consuming oil later. 

For me, it would be a waste of money to replace the converter if you're not going to correct the oil consumption problem, which likely means a replacement short block or engine.


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## vpanell (Sep 11, 2010)

Thank you smj999smj. I appreciate your reply. Sounds like I have a decision to make. The car has over 160k on it. With $ being tighter these days I may have no choice but to replace the cat and hope I get another year or so out of it. With that many mile on the car I dont beleive I want to add the expense of a short block.

Thanks again for the reply and for a great sight.


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## p4l1ndr0m3 (Sep 14, 2010)

Recommendations for pre-cat and cat replacements? Do the OEM units available now still have this problem?


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## vpanell (Sep 11, 2010)

I am back. I prchased an aftermarket pipe and replaced it. The car started and ran for a minute or so and died. Now it wont start. It tries to start but acts like its not getting feul or wont take fuel.

Now for the weird part. I changed the plugs, Bosch Platimums, because it was idling badly before the converter change. I removed one of the plugs so that I could check spark and when I bumped the starter over the engine started. It did not run well but it never died.:wtf:

I am totally confused now. It would start and run with a clogged cat but now it will not run at all. Could the cat under the car be clogged as well? Should I disconnect the exhaust pipe and see if it will start?

Any suggestions would be greatly appreciated.

Oh yeah, the check engine light went out as well. At least that is something I guess.


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## vpanell (Sep 11, 2010)

*Problem figured out*

Hey guys. I got the car running. The lower cat was completely clogged. I unbolted the exhaust and took the cat out(without breaking any bolts). Hit the starter and she fired right up. 

When I pointed the engine end of the pipe to the ground about a half pound of sandy looking material poured out of it. Now wonder she could not breath.

Since she started I guess I will invest in the lower cat too.

Thanks for the sight. I am sure I will have more questions later.


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## paul79 (Sep 14, 2010)

that sandy looking stuff would have been what was once inside your pre-cat...take it from my experience. My car is sitting in a parking lot for about a month now, with the new pre-cat sitting in the engine at the cost of $480...and if I drive the car around the building where I go to school (car made it here, and it's a technical school) the new pre-cat I bought starts glowing due to the oil issue...

I also had a completely clogged exhaust, and they ended up having to gut the secondary cat (the one under the car)...but it looks as though the damage was already done. Cross your fingers, keep an eye on your oil. I've got about 142k miles on my car before it was rendered a pile of scrap metal (unless NNA manages to agree to fix it due to the recall)

Granted, I have a 2003, you have a 2002...but it's the same engine, so the year doesn't make much difference


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## vpanell (Sep 11, 2010)

paul79 said:


> that sandy looking stuff would have been what was once inside your pre-cat...take it from my experience. My car is sitting in a parking lot for about a month now, with the new pre-cat sitting in the engine at the cost of $480...and if I drive the car around the building where I go to school (car made it here, and it's a technical school) the new pre-cat I bought starts glowing due to the oil issue...
> 
> I also had a completely clogged exhaust, and they ended up having to gut the secondary cat (the one under the car)...but it looks as though the damage was already done. Cross your fingers, keep an eye on your oil. I've got about 142k miles on my car before it was rendered a pile of scrap metal (unless NNA manages to agree to fix it due to the recall)
> 
> Granted, I have a 2003, you have a 2002...but it's the same engine, so the year doesn't make much difference


Yeah the damage is already done. It uses oil already but it does have over 180k on it. I did gut the lower cat as well.

I purchased my new pre-cat off line. It cost me $260 delivered and I installed it myself. If she wont pass inspection I will replace the lower cat as well.

I have to keep it running as long as I can.


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## paul79 (Sep 14, 2010)

I change my own oil, and had actually just changed it prior to my car no longer turning over at all due to the clogged exhaust. Two weeks after I had changed the oil, the oil light came on. Probably had put about 700 miles on the car since I had changed the oil. I can understand a car consuming oil as the mileage gets higher, but I thought that was a little excessive.

Granted, I have no idea at what point the oil light comes on. I know it takes 4 quarts of oil, but I'm not sure how much is left when the light comes on. I'm currently in the process of working on a complaint through NHTSA and trying to get them to contact Nissan to have my car fixed. To my knowledge, recalls are supposed to eliminate the problem, not just delay it. This is my third car, and the first time I've ever heard of a catalytic converter failing. I don't even recall my parents ever talking about needing that repaired/replaced. Transmissions, clutches, head gaskets, etc...but never a cat

Just wish I knew more about cars so I could argue with Nissan better


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