porsche 986 2.7 2000 hunting / idle issue

[Camscott98]

Hello, this is my first post in the forum, I am currently at trying to solve the following issue with my Boxster:

From cold: the revs will sit just over 1000 (1100-1250) then after about a minute will drop below to about 750/800 which is normal I think.
At the 750/800 stage the car starts to hunt and run rough at idle approx 500 RPM variance, which feels and sounds like a light misfire. Even when the car is fully warmed up out on a drive sitting at idle this will still occur. Applying the throttle back to the 1100 range will stop the symptoms. No Check engine light or any codes.

so far to try rectify the issue I have:

fitted new spark plugs
cleaned the throttle body (which was dirty)
cleaned the MAF (looked brand new before cleaning) I've unplugged the MAF sensor while running and it made no odds, still rough.
Changed the AOS (Air Oil Separator)
Checked for vacuum leaks (can't find any)


Other than the symptoms at idle the car runs as it should the rest of the drive. I understand there are other posts about this however I have read all I can and posting myself was a last resort! Any help would be greatly appreciated thanks.

[jonogt6]

Having experienced exactly the same problem that you have I'd almost certainly say that your problem is vacuum leak related. I d keep looking especially focussing on the throttle body connection...give those large hose clamps an extra nip up! Also check the large rubber o ring inside the oil filler cap.
Good luck!

[itsnotanova]

Originally Posted by jonogt6

Having experienced exactly the same problem that you have I'd almost certainly say that your problem is vacuum leak related. I d keep looking especially focussing on the throttle body connection...give those large hose clamps an extra nip up! Also check the large rubber o ring inside the oil filler cap.
Good luck!

X2. plus oil fill tube and hoses that go to the brake booster in the front.

[Camscott98]

I can hopefully have another look into it tomorrow afternoon! Its really becoming a pain to try and fix! thanks for the help ill let you know how I get on, the o-ring in the oil filler cap, how easy is it to tell if its causing the issue? Also the oil filler tube is this easy to remove? thanks