MSefi.com read only forum (Jan.15,2018)

Hello - I am working on a 3.0L 1980 Porsche 911 with MSII for a friend - it starts easily but the pedal must be pushed to keep it running - if I adjust the Throttle Body screw to get a higher idle speed it will run great when cold but the idle when warm will be too high. Have searched for vacuum leaks (3 different people have searched) and I even adjusted the throttle lever adjusting screw to allow the butterfly to close farther. The VE table is set to default - fairly lean but with no backfires.
1. Should I adjust the throttle level to fully closed and try that? any negatives to having the butterfly closed completely at idle? Will it even idle closed?
2. Any other things to cause this (other than vacuum or VE) ?
Thx -

What are you using for an IAC valve?

An IAC i not typically used on the Porsche 911. There's not one on my '74 which I installed 3 years ago (and have no problem with idle) and there's not one on the 80 911 which I'm working on. Same for the TPS - the software uses the MAP as a substitute for the TPS after a study showed the MAP follows RPM very closely.

Anyway - to answer your question - there is no IAC. Perhaps if there were one this problem could be fixed easier!

Thx

Yes, without an IAC you'll often have the engine behave like this. A lot of D-Jetronic systems used a similar device called an auxiliary air valve that works without a connection to the ECU.

Yes, the 911s re-use the AAR that was originally used on the factory installed CSI system. It's been checked and was found to be working - it's basically a controlled vacuum leak. It starts out open and as the engine warms it closes.

Thx for trying -

Larry