On my '87 951 when I first start the car in the morning it tries to catch the first time, stumbles, then stalls. Second try gets it but the idle will fluctuate for a few minutes. If I blip the throttle a couple of times it will smooth out. After those moments the car will run flawlessly the rest of the day. I don't think it's temp related as it's summer and fairly warm during the nights. This is a new issue and I've been doing some fixes lately. I've replaced most of the vacuum hoses and Y's (been very careful about hookup and routing). I thought there may have been a vacuum leak as the car has always had a slight high idle (after warming up) since I got it. In the past it would start and idle smoothly right at 950 first thing in the morning. Then after cruising the highway a few - the idle would bump up to 1150 or 1200. I thought there may be an issue with the TPS so I replaced that with a new one. That did not correct that issue and then after replacing the vacuum lines this new condition has begun. Last night I swopped out the FPR with a known good FPR and this morning I had the same problem a first start. What should I look at next? Fuel dampener? Idle actuator? I suspect it's vacuum related.

 

My guess is you have a leaking Idle Stabiliser Valve. Sort of a bi#@€ to replace without removing the intake manifold, but it can be done (at least I have). Do a search for ISV. Plenty of good threads on it.

Good luck!

 

Excellent Luis. Looking into that part/procedures.