Rough idle

[algin5109]

Started to notice a bit of a rough idle when I release the gas pedal. Tach drops down to around 600 and engine stutters for a sec then idles normally. So I just replaced the plugs and didn't make a difference. Only seems to happen when I get out of the gas. Any advice. Thanks.

 

[06 H3]

What year is your H3? I had similar symptoms

 

[algin5109]

06 with 3.5l

 

[06 H3]

Man, im sorry....

I have an 06 3.5L too. I changed the spark plugs and coil pack and still had a check engine light w/ misfire and a rough idle. Took it in and I had the dreaded cylinder head issue

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[algin5109]

Well, don't have a engine light on yet. Drive it till it don't move I guess. Than upgrade.

 

[M22KLARS]

I have an '06 3.5 and it's been doing that for about 3 years with no CEL. Eh..

 

[06 H3]

you guys are lucky then. Maybe a dirty MAF sensor or TB? I threw the codes and had the bad head and its getting replaced as we speak. Hopefully it isnt anything too crazy

 

[alrock]

Start with two or three gas tanks with Techron added and/or run Chevron through it, if you don't already. That clears up rough idle for many. I would also recommend cleaning the throttle body.

My truck was doing that as well and later down the road I ended up replacing the head. I would periodically get CELs with the code P0300 (general misfire) but I did not necessarily get those codes when it ran rough. In fact, the CELs never seemed to correspond to a rough idle.

 

[JonBishop]

I had that same thing happen, a case of bad gas and broken motor mounts, just like Alex said the chevron techron additive knocked it out, and my motor mounts made it really shaky and threw a misfire but when I went an took it to Zachs shop they helped me sleep at night knowing it wasn't the head... Sry 06 H3 hopefully u get ur Hummer back soon!

 

[Dennis]

Started to notice a bit of a rough idle when I release the gas pedal. Tach drops down to around 600 and engine stutters for a sec then idles normally. So I just replaced the plugs and didn't make a difference. Only seems to happen when I get out of the gas. Any advice. Thanks.

So did mine and I did the exact same thing..cept, mine finally, after maybe a year of doing that idle thingy..it threw a code, indicating a cyclinder misfire..it will happen sooner or later..I got a new head

..but read this post in another thread
http://www.hummer4x4offroad.com/for...-cylinder-head-(&p=37589&viewfull=1#post37589