afahrlan

The idle on my 951 hunts around quite a bit at times. It seems to have two different modes, one where it idles normally near 1000 rpm. In the other, which is the one I'm concerned about, the idle goes between 1250-1500 rpm and has on occasion idled upwards of 1750-2000 rpm. I've also noticed that when this happens, the revs drop significantly slower. A mechanic suggested that this was due to the temperature and was normal, but it has become more common lately and appears to be temperature unrelated; it's happened in temperatures from 40 to 100 degrees. Engine temp hasn't been abnormal when the idle goes funky. Any ideas?

Perry 951

Throttle Position Sensor, or a vac leak.

It could be shot, or out of adjustment.

Robby

I wish I could help you, but mine's doing the same thing. Mine will stick around 3500rpms when I back off the accelerater, and very slowly come down. It does idle a little high normally too. My throttle position switch was replaced about 6 months before this started, so I doubt it has anything to do w/it. Good luck and let me know if you find out what the prob is, and I'll do the same for you...

Perry 951

Try adjusting it. If the idle switch won't engage, the injectors will stay on during deceleration, and also have too much fuel at idle, causing a higher idle.

You can play with it and not hurt the car. You want it adjustd so it clicks when you crack the throttle, and clicks when you let off. Many are out of tolerance that I work on.

Mine did the same, and an adjustment took care of it.

Sean951

Try your idle stableizer valve. As they get older or more milage they get gunked up and stick causing the idle to "hunt" or stick in the rpm range you are talking about. If it were throtle pos.sensor it would be getting to much fuel on the bottom end causing stumbling under acceleration and puffs of blk. smoke. Loose vac. line would cause poor accel, stumbling, and low boost. Bad news is this valve is the big one under your intake that has all the hoses attached to it. Intake manifold must come off to get to it. This is a common problem on Audis & Porsches They can be cleaned sometimes with carb cleaner and brought back to life.

Melchior

It is true, the 951 Idle speed stabilizer is a bear to get to. If you can at least get one of the vaccuum tubes off, then you can spray some throttle body cleaner inside. I did this on my car last year. Let the cleaner sit inside for about ten minutes and then use a little high pressure air. The tire pump that came with the car works fine. You will not destroy anything inside the ISS since it is almost like a miniature Air Flow Meter that has a little door that slides open and closed.

andy b

afahrlan - did you ever figure this out? i'm having the same problem, idle hovers between 1000 - 2000 RPM at idle.

Deepice

You can test the TSP wit a volt meter look on paragons web sit for instructions

afahrlan

Nope, never figured it out, but my mechanic suggested it could be a vacuum leak as has been mentioned.

The symptoms sound like the TPS: doesn't cut fuel on deceleration, idles at ~1200 rpm and the car is a bit sluggish. Plus, flooring it/letting off a bunch of times usually seems to fix it.

But, the TPS clicks at the slightest throttle input (mind you, I've always tested this when the symptoms were gone) and clicks again when you let off.

Next time it happens I'll see if I get full boost and see if the TPS is clicking.

Thanks for all the suggestions BTW.