3.2 Pulsing Idle
 

On a ferw occasions the car at idle has pulsed up and down quickly about 2-300 rmp. For the first time at cold start-up it is now doing it, pulsing between 1400 & 1600 rpm. I let it run fow 5 minutes until the oil temp started to move then I ran it up to 3500rpm's and it seemed to settle down. Ideas?

John

See the following thread. I just fought with this problem for three weeks. I thought I had the problem fixed in the first post, but keep reading the entire thread.

http://forums.pelicanparts.com/porsche-911-technical-forum/174477-idle-trouble-time-fess-up.html

John,

My idle sometimes pulses at startup as well. I always assumed it was the idle stablization valve (ISV) not working quite right. Mine's never that bad where I actually have some sort of problem. More of an annoyance. I think it oscillates between 1000 and 1500 rpm for 10 sec. or so, before it finally starts to subside and settle into a steady idle @ something around 8-900 rpm.

If your car does this pulsing while @ operating temp., you can try to adjust your idle speed to address this issue. It's a good place to start.

http://forums.pelicanparts.com/porsche-911-technical-forum/6709-3-2-idle-speed-adjustment.html

http://forums.pelicanparts.com/porsche-911-technical-forum/155303-occillating-idle.html

http://forums.pelicanparts.com/porsche-911-technical-forum/91886-hunting-idle-warm-86-engine.html

Zoanas
I've fairly recently cleaned or replaced many of the components you did. I figured it was the mixture, but I thought I'd throw it out there. I've played with the mixture using a volt meter, but have not had it done with the gas analyzer. I've been debating on buying an analyzer or having my p-mechanic set it.

John

After thinking about the sequence of events with my problem, I am convinced that I had more than one issue causing similar symptoms.

Order of events:

Hunting Idle begins
Change Head Temp Sensor - no change
Change O2 Sensor - no change
Change ICV (installed backwards) - no change
Engine drop - http://forums.pelicanparts.com/showthread.php?s=&threadid=167070&highlight=Engine +Drop+Rookie
Change reference and speed sensors
Replace hoses, clamps, etc.
Engine reinstall - hunting remains - http://forums.pelicanparts.com/porsche-911-technical-forum/170738-scwdp-guys-help-w-carrera-engine-install.html
Remove and open AFM - noticed worn spot on potentiometer material inside, decide to refurbish
Install refurbished AFM without CO adjustment - hunting reduced, but remiains
Notice ICV backwards, corrected - no change

At this point I could stop the hunting during cold startup with the idle screw. This is when I decided to have my mech put it on a gas analyzer and set it correctly. VOILA!

I think that the worn spot on the potentiometer was causing it initially, and the mixture setting was the culprit once I got the AFM refurbished.