2006 H3 5cly. It starts to shake randomly only at idle. The car has 100,000 miles. In the last 5 month I replaced all spark plugs, and 3 coils. But before I use to get missfire cyl 1, or 2 etc, and I would replace the needed coil each time. now the p0300 code? I do have an aftermarket intake, but i dont see any holes. My battery is 4 years old, but the car starts fine, I ran an injector cleaner 3 month ago.

Interesting thing is, when I start the truck it seems to run fine but after 15-30 sec i get the missfires.

What can cause miss fires only at idle?

 

Was your head replaced?

 

Have you really checked you intake? Sprayed some starting fluid around the places it connects to ensure there are no leaks? Could an extremely dirty TB cause the random misfire?

 

When i press the gas, it runs perfect under load.

can a tiny crack in intake that i cant find cause such a problem? or does it have to be a large hole for the car to act up?


I have not replaced the head, it seemed to work fine. I dont have any recalls outstanding.

can an old battery or a dirty fuel filter cause this? what can it be?

Today in the morning I start the hummer and it works fine, no error code of shacking???? i am lost.

 

Find out if you fall in the Head issue.... 10000's did.... maybe more.... there are dozens that have had their head replaced just this year alone...