I haven't been on the forum for some time, hope I'm not rehashing a problem that'* already been solved.

Under part throttle, fairly hard acceleration from a stop, my '96 SE will accelerate well for a second or two, then the acceleration falls off, or goes flat. The car still picks up speed, slowly, but I can tell that it'* not accelerating like it should. The car doesn't bog down, and pick up again, it just seems to go flat. Once I get up to speed, it'* OK again under more moderate acceleration.

Anybody have any ideas as to why the car does this? I was wondering if maybe the coil packs are getting weak.

Anybody know the GM part number for the coil packs?

About 8,000 miles ago I replaced gas filter, air filter, plugs, wires, PCV and O2 sensor.

Anybody have any ideas? Thanks.

Dave

Sorry, in my last post for flat acceleration, I said my car was a '96, it'* not, it'* a '95. NON supercharged engine. Dumb!.

Dave

No, they weren't Bosch plugs. I think they were AC'*. The O2 sensor I got wasn't Bosch either. Everything was OK after I replaced the parts 8,000 miles ago. Started acting up more recently.

Dave

The SES light has not come on. I was also thinking maybe the catalytic converter is getting plugged. Any way to check Cat while it'* on the car? Disconnect exhaust pipe and look into end of Cat?

The problem has only shown up recently. Only happens if I accelerate fairly hard. Light throttle acceleration is normal.

Dave

Hey Dave. I had the same problem when i got my 94. mine would pull ok out of the hole then around 2500 rms on up it would fall short like you where saying. Mine never had the SES light come on so it was kida hard to find the problem. It would not down shift right.. It would not up shift right. When i had it to the floor it was shifting at like 3500rms. I tried replacing the TPS and made no difference. Then i replaced the EGR. The EGR made every problem that i was haveing go away. Everything was back to normal. Well i hope that this might help u a bit but from the way u discribed your problem i would say it is the EGR. Please let me know when u get the problem solved.

Good luck
Ryan

Thanks for the tip about the EGR valve, Ryan. I never thought about that.

My car does shift OK though, 5,000+ RPM under hard acceleration. Shifts normal under light throttle too.

Dave.

I have a 92 SSE Supercharged with the same problem also... Can i just block of the EGR? Or is that bad considering all the intake manifold problems I could incur.

I think I would agree. A clogged convertor will not set an SES light.

Measuring intake manifold vacuum is one test that the manual suggests for diagnosing a clogged convertor.

You'll run hotter cyl. temps, possibly burn a valve, they tried to run the N/A without it in 92, but that'* what happened. It won't help anything either.