jgk62

When I start my 951, it idles fine - just under 1000. But occasionally the idle will be really high - between 2000 and 3000.
This has happened to me twice. The first was when I took it to a garage for inspection. They said they couldnt do the inspection because the steering rack was leaking, and that it was idling really high. I got back in the car, turned it on and the idle was about 2300, never came down. Started it after about an hour after i got home and idle was back to normal.
I've driven it a couple of times (not hard) and never had the high idle occur.

Second time it happened was when I picked up the car after getting the rack replaced. Turned it on and the idle was at 2500. Got home, started it about an hour later - idle was fine.

I've searched the posts and found many possible causes such as idle stabilizer, DME, vacuum leak.
If it is a vacuum leak, would my idle always be high or kick in randomly?

The PO put in a Stage II chip - could it be related to this?

Thanks. Any and all information would be greatly appreciated!

John

Type_LT

I would suspect the chip, I've heard but haven't confirmed that people have problems with non name brand chips. Other things that come to mind are the solder joints on the DME, some get corroded or brittle and cause weird intermittent failures.

Bryan

Weird, my car does this too sometimes. It's an '88, 8-valve, non-turbo. I just went over the engine from top to bottom - new head gasket, lifters, belts, rollers, oil pan gasket, you name it. My idle air controller is new, all my vacuum line is perfect and there are no air leaks, I have a new ECU in the car (no aftermarket chips), the engine is perfect mechanically, new temp senders, etc.

And every now and then the idle is up over 2K. I can pull it back down with the clutch and it'll stay down but it's still a little floaty.

This seems to happen when the car has been putzing around in traffic and is good and warm. Just out zooming around on uncrowded roads, never happens.

My current theory is it's something in the charcoal canister purge mechanism. It's all vacuum and vacuum/temperature driven. More as it develops.

Bryan

jgk62

I started it today, idled fine for about 10 seconds then crept up to about 2300. I revved it real quick and the idle returned to normal for a couple seconds before going back up again.

Someone on another post mentioned tapping the idle stabilizer while it is idling high. Where is it located on the 951 and can i reach it enough to tap on it with a screwdriver?

Thanks!

tecart

high idle is a sign your tps is broken, get a new one and youll be all fixed i bet, make sure to adjust it so it clicks with the throttle opening and closing, tps sensor is my bet

David Salama

I have also had intermittent problems with the climbing high idle. Each time I could fix it by adjusting my Throttle Position Switch (loosen the two screws and move it until you get a click just as the throttle wheel hits the throttle stop screw) Also, try disconnecting the switch and lubricating it with silicone lube (dielectric gel). Good luck.

jeff951

Hi John

If it helps, i can send you my new TPS. i purchased it for my 88 951 and found out that it wasn't the problem. i have a similar problem but my idle just goes up and down 150rpm but is still close to the 850 rpm where it normally idles at. if it will help you, its yours. send me an email at porsche158@earthlink.net and i can mail it to you.

Jeff

Lizard944

What do your plugs look like? Carbon?
I solved my wandering idle by replacing the fuel pump regulator, damper, and TPS. Not sure which one was the culprit, cause I replaced them all at once, but now I have a sweet, steady 950.


Lizard

Bri Bro

I had a idle that would creep up, and I replaced the idle controller and checked every vacumn line but it still did it. One warm day I went to start it after letting it sit for an hour and it wouldn't start. After a weekend of checking every signal with a scope and a DVM, I determined my TPS wasn't working correctly. I replaced it and it not only fixed the no start problem but the idle was rock solid after that.