Man, it seems like it's just one thing after another here lately.

I've noticed that my '01 Impala (3.4L) feels like its struggling at low rpm. It's almost like I'm towing something until the revs come up a bit, and then there's a noticeable "boost" in power (I don't have a tach, so I don't know exactly what rpm the change occurs at). Up until this problem started a couple of weeks ago, the power delivery was always very even.

The problem seems to happen no matter what gear I'm in, but its most noticeable when starting from a dead stop. The only thing I can think of that happened around the time this started was this: I had the front of the car jacked up quite high for a day or so while replacing the right front brake line. On my first drive after that, the car bucked and sputtered as though it wasn't getting fuel. Then the check engine light came on with a code "P0102 - MAF sensor low I/P". The sputtering stopped on the next drive and the check engine light went out a few days later. Neither problem has happened again, but I've been noticing the power loss since then. Coincidence?

Any ideas?

 

Clogged cat?

 

Thanks for the reply. I thought about the cat...is there any way to verify that without taking it to the dealer? I have an OBD-II scanner, but I just got it, so I'm not sure what exactly it's capable of.

Also, I read about a GM "Special Policy #05551" which extends the warranty on the cat to 10 years/190,000 km for my vehicle as well as some others. My car should be covered by this, so I may be able to have that taken care of for free.

 

I guess a couple of easy ways (not necessarily the most accurate though) to check for a clogged cat are the following:

-When you increase RPMs in park you should be able to feel increased exhaust expulsion from the muffler... get a friend to help obviously
-Any rattling from the exhaust system at idle?
-Any soot on the piping around the Cat through to the muffler?

Im not sure if the Cats on these are welded on or not, but if not you can take it out and check it. You should be able to see through it with a light. If it looks clogged, or sounds clogged, its probablly clogged.

Some places can do an exhaust pressure test, but if there is a problem identified I dont think they can pinpoint exactly where the blockage is. But doing so will at least help you rule this out.

 

I called GM about a warranty replacement and they said that they would do a diagnostic, and if that was the problem the diagnostic & the repair would be free. If the problem was determined to be something else, I would have to pay for the diag. I'm actually ok with that if they can tell me what "something else" it is...

In the meantime, I'll try those things (as soon as it stops raining outside) and let you know. Thanks!

 

I unbolted the exhaust from the front of my cat and then took it for a short (and loud) test drive. You will know right away because it will run like a new car again. Then I took mine to the dealer knowing it was the cat and they replaced it, no diagostics charge that way.

 

Alight, here's an update. I was working on the cooling issue today, so I had the car running for awhile. I noticed that at cold idle, there's a rattle inside the exhaust which more or less goes away once it warms up. It seems to be coming from either the cat or the resonator. If I punch the gas , the exhaust sounds fine while its revving, but when I let off, there's a sputter/rattle sound again.

Finally, I noticed that if I hold the accelerator at ~2000 - 2500 rpm (don't have a tach, so thats a guess), the exhaust revs along with the engine for a few seconds, then sputters like I let off the gas (even though I didn't), then goes back to the correct sound. A few seconds later, it does it again...and then again. The whole time, my engine rpm stays the same. What does that mean?!?!

 

Have you checked for a clogged cat yet?????

 

MeowwwHackHack...yup sure sounds that way. Sauce, can you tell any difference in performance with your high flow cat? Just wondering.

 

"MeowwwHackHack...."