I have a very intermittent stalling problem. Occasionally after I am driving a while (engine hot), as I come to a stop/ red light, and push in the clutch pedal, the RPM's will drop down all the way to 0 and the red warning light "check oil " flashes on. The car starts right back up but there is always the fear that I will be left stranded. Any ideas?
1990 928 GT
79000 miles


Probably the idle stabilizer. You can sometimes clean it by spraying a solvent into the vacuum line on the driver's side of the intake. Check the archives for the detailed instructions.

Wally Plumley
928 Specialists


Hi Gary,

You should also check the idle switch. There are instructions in the shop manuals; if you don't have them I can write them up for you or fax them but I won't be back on the list for a couple days. It's quite simple, but you need an ohmmeter.

I just rebuilt the intake on my 88 S4 last spring partly to replace the idle switch for this problem. When the switch got hot, it stopped working, so the computer didn't realize it should open the idle stabilizer when I took my foot off the gas. It usually manifested a little different than your symptoms - the switch would spaz out rapidly jumping all over the resistance map from 0 to infinity. This set up a nice feedback loop and the rpms would oscillate wildly for a bit before stalling out. If yours is not working at all I can see this being the problem.

The idle stabilizer is interesting. The rest state is partly open so you can limp home if it breaks. As you apply a current, it closes then opens all the way. Unless it sticks at the closed (non idling) position I would think it should get enough air to idle. When you have this problem is it after driving on the highway for a long time or around town?

greg in Boston


Yes, my shark lives! Diagnosis confirmed - bad MAF. After reading the MAF FAQ on the site, I was even more focused on the MAF. The site specifically mentions that the MAF can malfunction due to water ingress, which obviously matches the trigger for my problem. So I decided to pull the MAF again and have it rebuilt.

Amazing, when I reinstalled the MAF and started her up, the symptoms of my problem had completely disappeared.