Help me out here, today started my car and it was idling weird. The CEL came on and it was a radom misfire. Checked the compression on the cylinders and they were fine. Changed the plugs and all seemed fine but the rough idling strted and the CEL came back on after a brief test drive. Well since the compression test was fine I can rule out valve problems. Can it be bad coil pack or shitty fuel?/?

 

Sounds like a bad coil pack. Would be nice if it was only one cylinder with a misfire because then you could move the coil pack and see if the misfire travels with the coil pack.

What was the fault the second time? The same thing?

 

Yes it was. Im thinking bad coil pack, also did a smoke test and no leaks were revealed and at least my valves are fine via the compression test. AS for a fuel issue, the car still takes off its just hesitant so I think a faulty injector can be ruled out

 

hate to sound like a broken record but check the cat

 

either coil pack(s) or cat

 

WHy the cat? The car isnt hesitating to bad. Wouldnt I get an o2 sensor code if it was the cat??

 

I hear what you are saying since a misfire can cause unburned fuel to get into the cat. I drove the car to the shop as soon as it happened. I will dirve it back tommorrow but other then that the car has been sitting. I thought the misfire itself would damage the cat, not the cat causing the misfire. WHo knows, I should find out more tommorrow