I recently purchased a 91 camaro rs convertible from a friend the car has set for a year and a half. My friend is not a mecanic by any means and parked the car because of the following problem. The car will run great light to light all day long, as soon as I cruise about 50 mph it has what feels like a miss but when I stop and start to accelerate again it falls on its face misses and chugs, the car has a bone stock 305 tbi I bought the car thinking easy fix nice cruiser, I replaced the distributor,ignition module, cap,rotor.My friend replaced fuel filter, map sensor ,plugs,wires,egr valve,tps,had the tbi gone through,and a few other things Im sure I forgot,I took it to a local garage he said it was bad selonoed (sure I spelled that wrong) for the lockout converter,local trans shop took it for a ride and he said he doesn't think thats it. The car will idle fine and it just broke 100,000 miles. I don't think its anything serious.Timing was set at 8 degrees with the wire unpluged. PLEASE HELP

 

How's the injector spray look? Even? Smooth?

The miss is most likely a lean condition. Maybe you could disconnect the MAP sensor to the throw the ecm into open loop mode and see how it runs.

 

If I unplug the elctrical connector on the map it runs just the same, If I unplug the vacuum line it dies.Thanks Hilts

 

Did you drive it with the map unplugged?

How does the spray pattern look?

 

Sounds like the EGR valve may be sticking open.

 

I think you nailed it.

 

The spray pattern looks good and even. The egr is new and I even cleaned it. I drove it with the map sensor unplugged ran the same,I replaced the map with one I had laying around ran great for a while, now its doing the same thing again. I noticed If its running like crap if I shut it off then start back up it runs good for a short time again.Then falls on its face, Its like some one just turned the distributor.Thanks Hilts

 

It doesnt feel like a rythmic shudder does it? Or is it an intermittent hiccup at cruise?

A rythmic shudder would most likely mean a faulty torque converter lockup, it could stay locked up when you braked or slowed, and would cause bad acceleration, but shouldnt chug and miss. That is most likely a fuel issue.

 

My 91 5.0 rs did the same thing, and it drove me batty. In the end i found it was the fuel pump sending unit, combined with a dirty filter on the end of the pump.I was suprised because i thought all the sending unit did was monitor the fuel level in the tank, but once i replaced it the car was fine. Found the sending unit on e-bay for 30 bucks, complete with a 225gph holley pump attached. Once i put it all in i never had that problem again. I also had a problem where the tach would jump wildly at idle and up to 2200 rpms. That turned out to be a bad distributor.

 

I have been driving the car around for the last couple of days with the esc wire unplugged It hasn't stumbled yet,and I have put about 200 miles on it.any ideas? Thanks to everybody who has replied with things to check.

 

something is horribly wrong if you pulled all of your spark advance and you think it is running better... what is your timing set at?

 

Timing is set at 6 degrees and it actually runs great just doesn't idle the best it will cruise just fine and if I mat it it will take right off?

 

From what you have done, and said so far, i think id be starting to look at the fuel pressure regulator. Buy an adjustable regulator, and change it up or down, and note any differences. You may also want to start replacing vacum lines, even if they look fine, a leak could be the cause of the heartache. I just remembered something about my car... look at the large hose runnijng from the vapor return canister. Mine was moving around, and making the car surge, and sputter. Once i found out it was moving, i just put a worm clamp on it, and it fixed it right up.

 

I have put about 350 miles on the car since I unplugged the tan wire with a black strip (esc) and it has not once stummbled, could the esc module be bad or knock sensor? If it was a fuel problem or a vacuum line it should still be doing it right? Thanks Hilts