928 idle problem

[jacek]

engine starts fine,runs fine for 10 second,after that it drop to
1500 rpm and then drop to 600 never ends.please help me.

[..P]

What year is your car? I have a '83 and can run through my replacements of Temp II sensor, Thermo time switch, etc. If it's a newer model I won't have "hands on" experience with it.

Right off hand it sounds like it "might" be the thermo time switch, mounted on my car up front where it's easy to get to, and it doesn't cost all that much either. The Thermo Time switch controls the cold start valve on a '83

P

[jacek]

my is 83' to

[..P]

Okay, hey, another '83. '83 was a great year, the 928 was the fastest car sold in North America that year (top speed).

When you say your car starts and runs fine for 10 seconds, does that mean you can start and drive away, or are you sitting and watching the tach.

It appears that you are sitting and watching the tach, so please clarify. Of course, the 928 idles below 1000 rpm, so I'm a little puzzled, and I'd appreciate it if you would restate your problem. If you are all of a sudden idiling down around 600 with no throttle response, then that's something totally different.

There is a big idle adjustment nut, actually a screw head about the size of a dime, in the front part of the motor in front of the spider intake, center of the motor. This can adjust the idle, but it sounds like you may have something else going on. I've had a few rounds with engine diagnostics on mine, so tell me again what's going on and I'll try to help.

thx, P