I have a Chevrolet 2008 Cobalt (LS) that I've had for about 7 years.
No sooner do I have this thing payed off, when it starts giving me the following problem (I've never had any trouble with it before).
We've tried everything we can think of, but to no avail.
- Engine light comes on. During regular driving, especially after idling, while trying to speed up, the engine light flashes. This usually doesn't happen (the flashing) once I get going on the highway. What's more, whenever the engine light is flashing, I can tell that the car loses energy (I say energy, but what I really mean is that the car loses acceleration).
- A simple computer reads "Cylinder 4 misfire."
- When idling (most of the time), the engine sounds pretty shaky, like it's on the verge of dying or not getting enough gas, etc.
- It shifts from 1st to 2nd pretty roughly, but not always, and when it does, the engine light is usually flashing.
- While accelerating to higher speeds on the highway and the engine is flashing (thus the acceleration is poor, as if it were only getting fuel from 3 of the 4 cylinders [<-- just a guess/just what it feels like]), eventually I reach a good speed and then it's like the 4th cylinder "kicks in" (or otherwise regains more accelerating power) and I feel the normal torque of the car and the engine light quits flashing.
- Now that it has gotten worse, it dies a lot while idling, at stop signs, at stop lights, and even sometimes when turning a corner and I'm not giving it gas.
- The above symptom ceases when I have the air-conditioner turned off (that is, the car has a much better time "not dying").
Here's what all we've tried:
- Changed the cylinder 4 fuel injector (twice in case we got a bad part).
- Changed the cylinder 4 coil pack (twice in case we got a bad part).
- Changed all spark plugs.
- Did a compression test on cylinder 4 (read a little low, 125, I think, but I was told "not enough to cause this."
- Tested the fuel pump. It tested just fine.
- Changed cam-sensor.
And that's all the symptoms and things we've tried that I can think of. I'm no car guru, but even our technician is having trouble figuring this one out.
I'm at a loss, as I've never heard of this problem before. Does anyone have any ideas what this could be?
Okay, since this question was posted, I've had the pulley and belt system replaced (it was aged a bit) and all 4 cylinders tested (they tested all about the same at approx. 125 psi, each). The problem still persists, though it seems a little better.