I have a 97 Z28, and I've been having this same problem for a while now. I can drive a distance (30-45 mins) and then park. Get back into the car to leave and it'll buck and stumble under application of throttle....Will idle just fine.You can get moving and then it will gradually clear out and run fine EXCEPT for lots of throttle application. Well the other day it did the stumbling and then just died and wouldn't restart. Got it towed to the dealership and they found fuel pressure to be good, not the opti, they noticed a P335, P336 code (CPS sensor fault- Replaced) and the harness that plugs into it.

Well they say the PCM doesn't see the CPS, but my car hasn't seen the CPS for 2 years because someone changed the motor and forgot the other internal "Reluctor?" for the CPS sensor to read. So they want to put a PCM on it.

Been talking to a few people and they say it sounds like a plugged CAT. I do experiance the dragging a heavy weight feeling sometimes, do smell the sulfury exhaust, and it smells really hot sometimes (Engine Cooling Fine).

Does this sound like plugged CATS to ya'll? Would knocking them out help? (Would be a great time for Long Tube Headers while I'm in there. (Would be for off-road use only ) Any ideas would be greatly appreciated because I told the dealership NO to the PCM.

 

Update....

I picked the car up from the dealership and it runs ok on the highway its acceleration that has problems. I can idle and then rev it up and it gets bad around 2500 rpms. If it sits for a while and cools down it'll run ok. I'm leaning towards plugged Cats because when I bought the car I drove it for 4-5 months with a burnt plug wire, and from reading past threads on here I see that will kill a cat pretty quick. One time I scanned it and it showed a restriction code in the cat and then it went away. Dealer said they saw no cat codes but I think they were just throwing parts at it. Just to replace the CPS sensor connector and do some diagnosis it was $363. If it was PCM it wouldn't run period right?


Any clues?

I really need help because this is a daily driver.

 

The CKP sensor is only there to detect misfires. The codes won't cause any problems, and it didn't need to be replaced. The engine will run fine without it.

There is no code for "a restriction .... in the cat". There are codes for low oxygen storage in the cats, not for a restriction. Ask the dealer to provide you with the specific code they found. You paid for a diagnosis, get the results.

You can check for a plugged cat by pulling a pre-cat O2 sensor, and putting a pressure gauge on it. The plugged cat will cause an irrationally high pressure.

 

I have not had a clogged cat, but my brother did on his 1999 3.8 V6 Camaro. That thing felt like it only had 75hp!!!! It would barely climb a hill and would not rev past 4000(if I recall). I could not believe how weak it was.....No codes at all. I tapped the bottom of the cat with a hammer and could hear parts rattling around.

When we pulled the cat....all the insides fell out of it. All we did was change out the cat and it easily picked up 80 hp....no joke. It also revved to 6000 no problem.