Lost 100+HP in 1989 Corvette

[vetterat]

I have an 89 coupe with 50K miles on it. The more I step on the accelerator, it seems the slower I go and was passed by a 4-cylinder Cavalier! The engine idles great. It seems to be okay for the first 2 miles of driving until it warms up. After warmed up and under acceleration, there seems to be more exhaust noise from the motor than the mufflers. No idiot lights.

Does anyone have an idea of where I start so that I may get the perfomance back? Catalytic converter?, crack in manifold?

 

[danny/'87]

i have an '87 and it had clogged cats, sounded like the symptoms you describe-idles good but not much response

 

[69MyWay]

Sounds like one of the three cats has a failure, if not more than one.

You can actually unbolt the center cat and get a look inside. You can usually jack the car up, and pount on the pre-cats with you fist (after it has cooled down). If you hear a rattle you KNOW they are bad.

Typical problem, and it will KILL power. I have gone through three Vettes now with that same failure.

Next question is....what to do?

Well, some people remove the entire exhaust system, take a cut off wheel, open the pre-cats up, gut them out, and have them welded back closed, and use a long wood boring bit or other device to pound the cat material out of the center one. Then they bolt it all back up for a otherwise stock look, but full free flow with minimal $$$$$.

However tempting it sounds, it is illegal. So, the next best option is to just get new ones. You will find most major Corvette retailers carry complete units. You can go through the Portal on the upper tool bar here to locate a vendor.

 

[vetterat]

Thanks for the advice.
I have the SEVERE rattle happen right as I lose power and then no power for the rest of the day. I have seen Y-pipes with attached precats for $299 from Mid-America. Looks like a good Christmas gift to myself!

 

[Ken]

If you hear it making noise but it's running ok, then it gets quiet and starts running really bad, it's the cats most likely. But then, you've already been told that.

_ken