Rough Idling & Accelerating

I have a 1994 V6 Chevrolet Camaro with ~197K miles. Recently I have noticed that after starting the engine it idles rougher than normal and also as I accelerate, especially between 45 and 65 mph. Several things have just been replaced and/or fixed: spark plugs, spark plug cables, oil, coil packs, water pump, & thermostat. I regularly use premium gasoline and when for some reason a lower octane is used I add an octane booster. Since this problem arose I tried a fuel system cleaner; it hasn’t worked thus far. The last time something like this happened, I took my Camaro to a trusted repair shop and when being diagnosed its’ cylinder chambers and many different lines flooded with fuel. After replacing the fuel regulator my car returned to normal. What could the problem be now?


Did that shop perform a fuel pressure test?

Did they perform an injector balance test?

Check engine light on?

If so, what are the codes?

IMO . . .the only way to properly clean injectors is to hook the tool up to the fuel, disable the fuel pump, and have the engine run off of the cleaning solution until it stalls

Maybe check the compression in all the cylinders and the idle vacuum. Something may turn up there, leading you to the problem. It does sound like some kind of air/fuel mixture problem. But there’s a dozen or more things that could cause it. You might get lucky and find it is just a vacuum leak is all.

With the spark plugs out and especially considering the high miles, a compression test should have been done. Cylinders that are getting washed down with raw gasoline can also suffer piston ring damage.

The easiest thing to do at this point would be to connect a vacuum gauge as that can provide an indication of engine condition. That can be done in seconds and could provide enough info about proceeding with a compression test.

I had a problem one time when the car wouldn’t start, and each time I changed something and I tried to start it, the fuel injectors would spray a new dose of fuel into the cylinders. They spray a lot more during cold starts, so it accumulates quickly. Eventually I fixed the problem why it wouldn’t start in the first place, but it still wouldn’t start, because the engine was flooded from the prior unsuccessful starting attempts. Once I figured this out, I had to remove all the spark plugs, crank the engine to blow as much gas out as possible, and let it sit overnight, then in the AM put the plugs back in, then it would finally start. Maybe something like that happened to the OP’s car.