Engine

Idle Adjustment on '83

>Is there a way to adjust the idle on my 83' 928S without having to take
>it to the dealer. I have looked for an idle adjustment and can not find
>one.
>Any help would be greatly appreciated
>Thanks
>Carl


First, be grateful that you don't have a LH-Jetronic system :-) Look down in front of the throttle body, you'll find a slotted adjustment screw. The head of the screw is about the size of a nickel. Clockwise to decrease and counter-clockwise is to increase. Use a good tachometer to do the adjustment. Do not rely on your instrumentation's tach. They're known to be inaccurate up to as much as 20%.

Some advice: Before you make the adjustment, make sure that you don't have any "false air" leak on the intake system. That is basically any rubber seal that you can get your hands on.

Tightening the intake boots on air plenum would be a very good start. Be forewarned that this action MIGHT cause the A/F ratio to be thrown off, so be prepared to make some A/F mixture adjustment as well.

Another place of false air leak would be the gigantic o-ring located at the throat of the air flow meter assembly. It's cheap to replace. You need to remove the air box in order to access it.

Finally, the vacuum servos buried within the dash/console is another cause of false air. Given time, the diaphragm within the servo will crack and leak. A common symptom of this problem would be inaccurate temp control of the AC and the ventilation system. There was a long thread on this subject a while back, so you should be able to get more info from the archive. Good luck.

Vince Yu
'78 928
'83 928S