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Discussion Starter #1
Greetings!

I have a 2008 Cobalt coupe with 75000 miles. In the past few months I've had issues creep up and haven't been able to isolate the problem.

-Started as cylinder 4 misfire, randomly.
-A few months later progressed to rough idle while in drive (mostly if I was stuck in a long drive through or stop light).
-Now I currently get the rough idle, and the engine starts shaking and the car stalls out if I don't move. If I put it into neutral/park, it stops, but starts again in drive until I accelerate.
-When the engine gets to shaking, I get traction control alerts and the check engine light flashes.
-If I turn the car on/off-it all goes away until the next idle.

So far I have replaced the coil pack/spark plug for cylinder 4. Vacuum leak check, replaced the camshaft position sensor. We've cleaned the throttle body and a few various other things we found mentioned on different forum posts.

Can anyone shed any light on something I haven't tried, or that we might be missing? Our next step is O2 sensors, I think. We gathered a list and are just going down the line at this point of others with the same issues.

Any help would be greatly appreciated!
K
 

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It's always just cylinder 4 that's missing? Did you check the injector? You could even just try swapping it with a different cylinder, if the miss moves to the other cylinder you know you found your problem and if not you didn't waste any money replacing a good part.

---------- Post added at 02:53 PM ---------- Previous post was at 02:51 PM ----------

Another thing would be to do a compression test, if it was the o2 sensor I would imagine it would have misfires on all cylinders and not just 4
 

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It's always just cylinder 4 that's missing? Did you check the injector? You could even just try swapping it with a different cylinder, if the miss moves to the other cylinder you know you found your problem and if not you didn't waste any money replacing a good part.
Always 4. I've moved them around to every other slot, and its ALWAYS 4. We moved the coils and spark plugs around, and it is consistently 4. My brother just said that he hasn't checked the injector though.

Thank you for your reply! We will check that now :)
 

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Alright, yeah check the injector out and if that isn't the issue I would absolutely do a compression test

---------- Post added at 03:02 PM ---------- Previous post was at 03:00 PM ----------

Other than that, I suppose it could also be the wiring for cylinder 4 injector or coil pack as well.
 

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Alright, yeah check the injector out and if that isn't the issue I would absolutely do a compression test

---------- Post added at 03:02 PM ---------- Previous post was at 03:00 PM ----------

Other than that, I suppose it could also be the wiring for cylinder 4 injector or coil pack as well.
So...most of the issues turned out to be a bad MAF sensor. Still throwing the cylinder misfire, injectors have been swapped to see if the misfire follows it. Thanks again for your suggestions!
 
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