I have a 97 3.8L camaro RS with manual transmission, and I've been having acceleration problems. When i push the gas pedal more than just a little bit, the car starts to stumble and hesitate and it just won't accelerate normally. But if i do not depress the gas a lot, i can accelerate slowly and without any stumbling and hesitating all the way to highway speeds, and through all the gears. But if i give it any more gas than only about a quarter it starts stumbling; it will still accelerate but it is violent and not smooth and feels like it is hurting the engine. Air filter, fuel filter, cables and coils have been changed (though not the spark plugs, i think--which i hear from other people is kind of strange, but i don't know why exactly he didn't try changing the plugs): that was all due to my mechanic hitting and missing while trying to fix the problem. So if anyone would have any idea what exactly might fix the problem so that i can tell a mechanic to just fix THAT and to not guess at the problem, i would appreciate it very much.
thanks in advance
p.s. once i had poured in 91 octane gas (i usually use 87 because that is what the manual recommends) and it felt like the problem went away and i celebrated for about a day thinking that i had found the solution, but after a bit the problem came back, and i'm not sure whether it was because the next tank of 91 might have not been as good as the one that i thought fixed the problem, or perhaps there was no real connection here at all between the 'better gas' and the problem going away.

 

Did your mechanic scan it for any codes? If not, he needs to start there! More than likely the reason he didn't change the plugs is because it is a royal PITA. First check for codes. There are alot of things that could be causing your issue at this point.

 

Oh dang I didn't even notice you posted here as well.

I had the same problem with my 97 RS (an automatic) and it turned out to be back coil packs.

 

We can not tell you whats wrong with your car. The symptom you described can be cause by weak spark and timing issue or a lean condition. All we know is combustion is failing under load. That means we have narrowed it down to something in the engine or something is the ignition or something in the fuel system. This is why your mechanic is guessing. There are mechanic out there that will not have to guess.

To a driveabilty tech telling him your car stumbles under acceleration whats wrong with it? Is like going to a regular mechanic and saying "my car makes a noise going over a bump. What is wrong with it?"

 

Bad coil pack, spark plugs, or clogged fuel injector but least likly. Did he replace all the coil packs? Thats alot of money for things that didnt fix the problem.