Hello, I just got me a H3 Hummer, it is a 2008 with 85000 miles. I notice that at idle in gear or not the engine idles so rough it vibrates the steering wheel. So hear is what i've done so far , changed spark plugs , cleaned throttle body, cleaned maf sensor ( mass) , running hgh test gas and also putting heat gas treatment and sea foam , changed air filter. Still have problem , does any one know if I've missed any thing or know what to do? One other question could it be the in tank fuel pump? thanks for any help.

 

1- Did ya' take the TB all the way off to clean? It needs thoroughly cleaned on both sides.

2- Did 'ya Seafoam before or after the spark plug change? A Seafoam treatment can possibly foul the plugs.

3- Any recent codes?

 

Correct GAP on the plugs? What kind of plugs? Purchase a new coil pack/install and move it around to different cylinders and see if you have an effect on the issue. Check for vacuum leaks all around. However...the I5 vibrates a little more than "normal" due to its nature....

 

Didn't clean both sides of TB , ill try that. There have been no codes. After doing all that I did it did seem to get a little better, but I didn't know that it was normal for this engine. Thanks for the reply.

 

Could be a bad cylinder head. I have an 08 with 60k and mine crapped the bed. They had soft valves and had to replaced the head. Mine popped an alarm saying misfire of #5 cylinder, but started out with rough idle. Common in the H3.