An Interim Update on CIS Issue

Good evening,

After working on the car for a good part of the day, I took it for a drive with my tools, and made adjustments while cruising around town. I found that when I got the mixture adjusted, tightening down the retaining nut changed the setting, so it took me a good 10 minutes in a grocery store parking lot to get it ironed out. I still feel it may be slightly off.

The car seemed to run perfectly when fully warmed up, however I haven't had a chance to test the configuration with the car cold.

I left the car sit for 3-4 hours, just went to bring it into the garage, and it wasn't easy to start. Before I began this process, it would "fire" immediately. Now, it turns over for 2-3 seconds before starting.

The car started and stalled 3 times before idling. It idled low, and the engine speed wandered back and forth, however not as dramaticly as it did previously. Pushing on the gas to rev the engine and releasing it caused the engine to drop well below 1,000rpm's and stall. It would then turn over for 3-4 seconds then start. When started, after revving the engine and releasing the throttle, I could baby the throttle a little, and it would then idle at around 900rpm without intervention, although the idle speed does wander. Interestingly enough, the wandering seems to appear in intervals; the car will idle ok for 30 seconds, then the idle will wander for 30 seconds, etc. etc. Turning the A/C on caused the engine to stall.

When I adjusted the mixture, I also adjusted the idle speed to 1,200rpm's (works out to around 900rpm-1,000rpm with the A/C on).

So, it seems I'm still having some unusual cold start behavior. I plan on testing the car again in the morning when it's completely cold.

I'm wondering however if the Auxiliary Air Valve could be defective or out of adjustment, because shouldn't the car idle slightly high for a little while while warming up? Also, now that I have the vacuum hose routing corrected, and everything adjusted with what seems to be good control pressures, what could be causing my continued cold start issue? Could the mixture be off enough to cause this problem? Other ideas?

Thanks!

Michael

"I found that when I got the mixture adjusted,tightening down the retaining nut changed the setting"

What retaining nut are you talking about? Are you sure you're adjusting the mixture correctly? I don't recall a retaining nut.



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Bill Krause
'79 911SC Euro

I have been following this post for a little while and everthing that is happening to your car is EXACTLY what my car is doing and I also tried playing with the mixture and I can get the car to idle now when warm but it seems to run rich when cold and I have to use the gas to start it when warm sometimes.I am very interested to see if your car does the same thing as mine when you try to start it tommorrow morning.

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Grant 75 911 targa

If I remember correctly, my CIS was doing the hunting thing when cold. It also had a rough idle. What I ended up doing was to rub some vaseline on the pop off valve seal and lubed the spring on it. (no comments from the peanut gallery). Runs great ever since.

Hope this helps
Tim in Sac

1200 rpm is too high for idle speed. have a shop set CO at 3.5%, at 1000 rpm. if it still surges cold, then the warmup reg. is starting out with too low pressure. also set the ignition timing to 35 degrees total advance, regardless of where that leaves the idle timing setting. you need an adjustable advance timing light to do it.