Weird idle after spark plug change
 

Well had a rough idle and every forum was saying change plugs. So changed with oem plugs (Ac delco). Now with no check engine light it's going back and fourth between 500-1000 rpms as im slowing down to a stop and I can feel the Ac increase and decrease as rpms change. I figured it would throw the check engine light with this but no luck. It has died at a stop and while reversing at slow speeds. Once im on the road drives perfect. If this sounds familiar to anyone please post. Thanks in advance!!

This is on a 2006 h3 w/ 76k miles!

Has your head been replaced? The 2006 H3s with the 3.5l had head problems. Mine went at around 30,000 miles and was replaced under warranty. It started as a rough idle. It took some time before the check engine light came on.

This issue is becoming more frequent! had the same problem with my 06 and although I havent nailed it down entirely, it appears to be related to the cheap electronic sensors. Did you do a TB and MAF clean along with your spark plug change? Remember to only use MAF cleaner not carb cleaner like I did. (probably ruined the darn thing, by evidence of continued intermittent rough idle)
Also by removing the TB and giving it a thorough clean down with TB cleaner will improve the function of the Throttle Position Sensor. (Im guessing this is whats causing your fluctuation engine RPM)

No offense brachilius but everyone always jumps to the engine head problem but the prevalence of that issue is not as vast as folks are making it out to be. Not to mention the fact of GM choosing to put cheap electronic parts on the MAF and TPS. At least they went with Delphi on the coil packs!

Oh one more thing, did you reattach the valve cover breather hose to the engine? I forgot that when I did my plugs and got all kinds of codes.
Here is a post of my spark plug change WITH PICTURES! Hummer X Forum • View topic - 06 H3 Spark Plug replace, w/pics

Have you brought this to the attention of your local dealer? I can also look into this for you. Please private message me with your contact information, VIN, and the name of your dealer and we'll look into the matter further. Thank you in advance.

Tricia, GM Customer Service.

I have the same problem did the same thing when i got the truck
changed the plugs (OEM) still ran like $hit got on line found this forum :)
if i had did some research on this year an the problems it has i whould have
looked for an 07 H3 love the truck hate the rough idle thinking about
dumping it off on a dealer for a H2.

Give it a rest Peggy!

I had the same issue on my previous '07 (early build) so it's not just the 06's. Dealer first replaced the plugs, second jumped the coils and replaced one of the coils, eventually the CE light came on so they did a fuel injection test then flush. Rough idle continued and CE light kept coming back. The final trip they replaced the head...problem solved. Ran like a champ so I traded it in:D.

hi Diablito
I too have suffered the H3 idle sydrone. the H3 had a problem with the bonnet louvre leaking onto the coil and one of the spark plugs which started off as rough idle at stops which even stalled completey and needed to be restarted. it even had to have the accelarater pedal feathered while stationary to stay idle.the Gm dealer after fixing the coil and louvre problem noticed that the absolute pressure sender manifold switch was faulty. had it replaced and that was the end of my idle issues. my trucks a 09 plated H3 with 13000kilometers on the clock

Inspect the Camshaft Actuator Solenoid.

First off I want to thank y'all for the quick responses. Well when I had everything apart I did notice the tb was dirty so that's my next step. Is it ok to take it completely off and also is it ok to move the throttle plate by hand? Any thing I should look out for? Well also when I had the coil plugs off I noticed some white corrosion. I guess caused from moisture. Can I clean that off myself or is it shot? I'd hate to cause more damage that good. Thanks again!!

Also I have not had any head work done if idle is still rough after tb and maf cleaning that's my next step.