Cold start idle issues?
 

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.

You have covered two of the things I would have done as well, vacuum line and TPS. My guess is the ICV/ISV or the hoses connecting the part have cracked and there is a leak at the bend.
TexasBlake just did a post on checking and I did a link:

http://forums.pelicanparts.com/showthread.php?t=481223&highlight=idle+control+val ve

GL
John_AZ
1988 924S + 1987 924S

Copy that John. From what I've read so far... it's a real beast to get to without pulling the manifold. $10.75 for the hoses, $162.25 for the part... ouch!!!

question u gotta ask yourself, is $170 really worth it to not have to press your foot on the throttle a little when starting cold :)

Well, they usually get worse....

But often the Porsche ones can be cleaned (degunked) or one can get a used one.

I've got two OE Bosch ICV's, never used. I had been keeping them as spares but after 3 years I havent needed either. YET!. Asking $120/ea

I know as soon as I sell them....grrr.

PM me if interested!

Jim :D

Would SeaFoam clean the ISV?

http://www.seafoamsales.com/motor-treatment/index.html

I've used it on my 924S and 944S for general valve/injector cleaning but was wondering if I was able to introduce a few ounces upstream could that cleanse the ISV? If we think that's a good idea - which would be the optimum hose connection to get the liquid into the system? For intake valves the instructions say the main vacuum hose off the brake booster.