rough idling on 986S
 

hi all,

I'm experiencing idling issue on my 986S, manual transmission, 80K (AOS is new, only 2k on it). I'm thinking of changing MAF sensor and clean throttle body, but before that I would like to see what you guys think about. Attached picture is RPM graph that I captured with my phone.
Thanks.

Regards,
Armen

http://986forum.com/forums/uploads01/rpm1444066182.jpg

Clean the MAF. I got mine wet/dirty a little while ago, and not only did it idle poorly, it was throwing misfire codes. Got the MAF clean and dry, and all issues were gone.

Perhaps a vaccum leak ..?

Looks more suspect than a MAF, since the idle is consistently so low. I would think there is a vacuum leak somewhere. Do you have any fault codes stored?

If it were just MAF instability, I would expect a more average RPM of 750.

I had a similar issue, similar mileage and AOS just replaced as well.

For me it was a pinched seal on the new AOS. Make sure everything is hooked up well back there.

Despite the pinched seal I didn't have a light thrown for a long time after the AOS was installed.

guys thanks for input.
I dont have any codes, everything clean. I opened engine oil cap when car was running and RPMs jump up about 100-150rpm.So I guess its not a major vacuum leak or could be a small leak? I changed AOS myself last year and the main reason I replaced it was idling.I never cleaned throttle body and MAF since I purchased car back in 2013, maybe that a good place to start.
Thanks.

It could be a dirty throttle body, which has a hunting idle as one symptom. Saw this on my 01S. Once the TB was cleaned the idle returned to rock steady.

Certainly clean the TB and MAF first. Pretty easy to take the intake tubing/MAF, TB off and spray around with MAF cleaner. A battery disconnect normally helps after cleaning MAF and TB too.

Taking the throttle body out is easier when it's warm. You're lucky that you are in LA. The rubber stuff is a ******************** when trying to get the throttle body back in.