Just a curious question what does the HHR idle @ with warm engine in gear mine idles at about 850/900 I am thinkin this is high btw the Ac on /off makes no difference .I am lookin for the reson the mpg feel off , recent drop from 29/30 to 27/28 I just tried Seafoam I normally do not use such stuff , But I am tryin Thanks in advance

 

as far as the mpg drop, oil change up to date?
my idle is right around there too. fwiw.

 

You are within spec with your idle speed according to the service manuals. The reason engaging the A/C makes no difference in idle speed is because the ECM automatically compensates for the load of the A/C compressor when you push the button, hence no rpm drop.

A drop of 2 mpg could be down to the higher Summer temperatures, possibly increased rolling resistance due to under inflated tires, reformulated gasoline sold during warm weather months, or a half dozen other things.

How many miles do you have on your HHR, when was the air filter last replaced, is it due for a plug change, or have your driving habits or route changed? Just some of the things you need to consider when chasing a mpg drop, I wouldn't be overly concerned by a mild drop in mileage as it doesn't take much to skew your overall average.

 

Is it humid where you live?

 

Miles?

 

Mine idles 600, with air on 700,

 

Thanks guys , the hhr has a bit over 130,000 miles i do hva e the oil change up to date , i run amsoil , the air filter could probably stand a change the humidity well this is the south , I am thinkin a stuck idle motor

 

Clean your throttle body. It will help.

 

Interesting..since things warmed up, mine is getting 2-4 mpg better...been getting some good milage lately, even when I pulled the bike....with air on

 

I cleaned my throttle body when I did the GMPP swap, wasn't having any issues before & none now, just a bigger grin looking under the hood..

& mine idles at 800-850 rpm.. And gas mileage is super..