returning here for more help. my'88 s4 has been stalling lately at lights while idling. recently had the fuel injection computer replaced. is it a simple procedure to adjust the idle setting? it used to idle at about 800 rpms now it's less. is 800 the proper number and can i save a trip to the mechanic and do it myself? not much with tools here but willing to try. thanks

 

You probably have a vacuum issue more likely. Check Rennlist archives to find test procedures.

 

Cranky-

The idel speed should be 675 +/- 25 rpm on the 87+ S4 Models.

The idle speed is completly controlled by computer with no adjustments.

For a high idle speed - a few things can be involved....however - for a low speed, I would tend to think of the LH Brain settings - non of which are adjustable.

Just out of curiousity...where did you get the rebuilt/used LH Unit?

 

bought lh unit new from porsche

 

You might have a faulty idle regulator. To replace it, the intake needs to be removed. This is so much work that you should do preventive maintenance while the intake is off. Specifically, the following parts should be replaced along with the idle regulator:

- Knock Sensors
- Throttle Position Switch
- All Vacuum Hoses

Since the injectors have to come out, this might also be a good time to have them cleaned.