Thanks for the advise. I will check the rubber boots for gaps / leaks.

 

I'm going through the same process:misfire when cold on all cylinders, maybe a little rough idle. After I clear the codes the CEL comes back in 250-400 miles. I' ce changed the plugs and coils with no change in the pattern. My car is a 05 C2 with 36000 miles. I got it last year in Aug with 22000 miles( I drive it almost daily... I had it with my mechanic but after a week they couldn't reproduce the problem. I used Mobil, Shell, BP gas but the codes come back. At this point, I don't know what to do...

 

I continue to advise having the fuel injectors cleaned. Mine did this and after the cleaning runs perfect, no issues in over a year.

 

Cleaning the injectors sounds logical. I'll ask my mechanic if he can help me with it.

 

Thanks Hattrick. It appears that one of the hose clamp was loose and leaking air. No more codes!!!!!,