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scaldeddog · Joined: 05 Sep 2011 Posts: 8 Location: Central Florida

When I start the car cold, she will idle fine. After it warms up and I come to a stop light, the idle will raise to 1400 then back to normal and will continue to bounce back and forth until I take off again. It only does it when it gets to operating temperature. Any ideas?

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Vaccuum leaks, worn AFM, bad IAC, bad baseline idle setting, bad FPR?
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

scaldeddog · Joined: 05 Sep 2011 Posts: 8 Location: Central Florida

This is truly the mystery car...

Mystery 1! I drove the car to work today and it surged once at a stoplight then remained about 1400 rpm. I dont think it's a vacuum leak, I checked for that earlier. When I first got her running the idle was very high, about 2300 after warm-up. Changed the TPS which got the idle down to about 1400 then changed the ICV which lowered it to 900. (Both the ICV and TPS were parts from spare cars.) As it warmed up the idle would increase to 1000-1100 rpm. However, once I drive it and 5 or so miles, the surging would start. From 1100 to 1400 and back. Even before changing the ICV and TPS, the car would surge when it was warm.

Mystery 2! On three seperate ocassions I went to start the car and there was no spark. This happened 2 days ago the last time. Today I sat in it and it fired right up without changing anything?

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

Sounds like the timing is drifting somehow? The computer is trying to compensate.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

edredas · Joined: 09 Dec 2004 Posts: 861 Location: Charlotte, NC

Surging idle when the car is warm is most often caused by the idle set screw being adjusted without first jumping the diagnostic plug.

http://www.clarks-garage.com/shop-manual/fuel-08.htm
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'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver

scaldeddog · Joined: 05 Sep 2011 Posts: 8 Location: Central Florida

I think that's what it was cause it's working right now. It still doesn't start at random times thought; like when the wife tried to take our daughter to the bus stop this morning.

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

What is the condition of your speed/ref plugs and wiring?
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

scaldeddog · Joined: 05 Sep 2011 Posts: 8 Location: Central Florida

Most of the wiring is good. I know there is a dead short somewhere with the left low beam, and I have found a temperamental plug for the left taillight assembly but I think I have that fixed. I think the starting issue is a connection in the engine compartment on the firewall behind the intake. The engine would turn but no spark. The starting issue from yesterday is new. When the key is turned nothing would happen. That is an ignition switch issue I believe.