rough idling on 986S - 986 Forum - The Community for Porsche Boxster & Cayman Owners

ArmenT · 10-05-2015, 09:32 AM

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

pony13ca · 10-05-2015, 10:06 AM

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.

Gilles · 10-05-2015, 10:32 AM

Perhaps a vaccum leak ..?

epapp · 10-05-2015, 12:03 PM

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.

BIGJake111 · 10-05-2015, 12:26 PM

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.

ArmenT · 10-05-2015, 04:12 PM

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.

thom4782 · 10-05-2015, 08:03 PM

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.

epapp · 10-06-2015, 07:31 AM

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.

nieuwhzn · 10-06-2015, 08:28 PM

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.