p 305 code

[signals34]

i have a 2006 h3, about 120,000 miles....getting that 305 code, but only when i let idle for about 2 minutes........driving normal, no codes, and it runs fine...no code,after clearing it.....highway speeds, good power, no lag.....any ideas....i did put all new coils,plugs,new maf in....thanks

 

[rascole]

swap coil #4 & 5. see if the code changes. Then check spark plugs.

 

[Happy Hummer]

I'd just get new ac delco c.o.p
06 H3 (I5 3.5L): 12568062, 8-12568-062-0

06-07 Spark Plugs: AC Del 41-103
Gap is typically set to .42-.43

Run some Techron system cleaner.

 

[alrock]

Did you use AC Delco plugs or another brand?

 

[signals34]

did swap 4 and 5 coil, 305 still comes up....used delco plugs....was able to tighten 4 bolts on the intake manifold...funny i ran it for 3 weeks perfect, no code.......i started it up one morning, forgot something, ran inside and when i came back out the check engine was on, 305 code...lol...it idled for about 3 minutes...no clue...lol...