I have a 07 hummer h3 3.7L. whenever i go to slow down the idle will jump up and down, clear down to 400 rpms or less and just about dies. and then shoots back up to 900 and back down. does it all the time. it idles fine sitting still and taking off. its whenever you give it gas and let off it does this or slow down. i have read alot about the cylinder head problems on the 06 hummers and i dont wanna jump towards that. im hopin someone can just figure the problem out. plugs are new, its always serviced and tuned up. i do throw a check engine light every so often. i mean 2 months later at a time, i pluged it in at advanced with their computer and the computer says it is not plugged in. im confused, i have no other place to get a scanner other than going to the garage and i dont have that kind of money till spring. any help would be appreciated. thanks.

 

roughneck... welcome to the forum... introduce yourself in the new members section... I would do the trouble shooting first... air filter, replace if dirty or old... check the throttle body, clean? MAF sensor is a little whinny biatch and could be fouled up as well... if the plugs are new, what brand are they? OEM seems to be the best...

I have the same symptoms on mine and I went out and picked up a scan gauge II on fleabay for under $100... codes are far in between but I do stall out occasionally w/o code... volts have been dipping... so now Im looking for a aftermarket hi output alt...

 

well i always clean my throttle bodies on every vehicle i own. i neglected the hummers and that was the problem. thanks