Idle very sporadic for several minutes after startup

Doesn't seem to be related to being cold, but is related to how long since startup; or I guess, since just sitting.
The idle fluctuates tremdously for several minutes, and if you're not careful, it might dip down and stall (like if you drove to a the first light of your journey and slowed quickly to a stop).
What gives?

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Kurt B
1984 911 Carrera Cabriolet
75 914 1.8

Sounds like a vacuum leak.

Kurt,

I have an 85 model and if the idle "hunts" after first starting then you may have the same thing I did.

Mine went from 600 to 1500 rpm and just cycled back and forth, finally settling down a bit when warm but not totally. It would return from time to time to normal but usually sounded like the motor had a set of race cams in at a stoplight sometimes with its loaping idle!

There is a valve in the very front part of the motor (rear of the car) when opening the rear deck and from my newly installed PET program, the part appears to be: 930 606 161 00 and is called the idle stabilizer I believe.

Best $100 or so I spent and cured the "hunting" idle immediately. This MIGHT be the same problem as on your car. I would try to find another DME car and switch the valve out as its easy to get to and will show you right away if this is the problem.

Good luck,

JoeA

My '85 has acted great in the cold weather, so I haven't had the problem myself, but I've read a lot on the Idle stabilizer (control) valve with regard to my Volvo (it was doing a bit of hunting at idle as well)
The valve regulates the air flow around the throttle plate. You'll recognize it as it is attached on either end by rubber hoses which permit the regulated air flow around the throttle plate.
You may want to take it off & look inside & shake it to see if its movement is restricted at all. Check also to see that its wire connector is attached properly (or broken or corroded)
Don't know of any electrical check that will determine if its operational... what I've read suggests to replace it with another component (off another car, if possible)to see if that's the problem. Good luck.
regards,
jlex.

Okay thanks guys. I'll check that out. Doesn't sound like an expensive part to replace.

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Kurt B
1984 911 Carrera Cabriolet
75 914 1.8

There have been 'issues' for years about the cylinder head temperature sensor at cylinder #3. The computer in the DME unit has difficulty if the sensor goes bad ...

It is not an inexpensive part at $54.30 from Pelican, but it is worth checking.

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Warren Hall
1973 911S Targa