With the car not in gear generally when its cold returning to idle it dips down then quickly jumps up to idle. Today was the first time it has actually stalled, every other time it has just come close.

What could cause this? I'm thinking its either my ISV or my chips that are mapped for 55# injectors just aren't correct.

 

Sounds like an ISV issue, I got rid of mine,, idles much better...when warm of course....

 

My car did that when the ISV started to develop a leak. Reached a point where the car would not hold an idle. You can reseal it with RTV, but it's probably better to just replace it.

 

Is this a MAF equipped car?

When did it start dipping? Suddenly?

 

Its been doing this for a few months now just keeps getting worse. When I had my intake off in october I cleaned the ISV out and sealed the seams with epoxy. Whats the difference between the ISV with the 930 part number and the one with the 965 part number? Different companies sell them for 944s.
No MAF, for now at least.

Also, what is the way to go about setting idle with the test port? Maybe that will fix my problem.

 

I'd check for vacuum leaks. Compressed air is the best way.

 

http://www.lindseyracing.com/mm5/mer..._Code=IDLE944T

 

Dunno. I just got a new one from Bosch. Part number: 0 280 140 501.

 

Its probably worth checking your idle adjustment screw (in throttle body) before you get too carried away with ISV replacement. When I put my motor back together recently I deleted the venturi setup as one of the while I was there tasks. Anyway when I got the motor running I found that the idle rpm dropped a fair bit when coming to a stop etc. The ISV took about 3 cycles before the RPM would stablise. The reason for that was that the venturi setup was providing some bleed air and by removing it there was less throttle bypass air to maintain idle. Opening up the idle screw a little resolved that ie RPM drops to 800 or so and stays there.

 

Very true. I was assuming he had already attempted all manner of adjustments to the idle screw. I know I did before resorting to the new ISV!

 

Keith, let me know if the Lindsey Procedure fixes it. As you may remember I have the same problem, and it has caused my car to stall out once.

 

The Lindsey procedure for setting the idle works great (jumpering ports B & C in the DME diagnostic socket) but it won't make up for a leaking ISV.

 

Can you just remove the ISV altogether? Or...is LFA being sarcastic? How does this affect overall drivability? My car has always died following abrupt throttle release from higher RPM's. I have long suspected my APE chips and MAF are responsible for this problem, but I'm about to rule that out (have a new Vitesse kit in my garage now).

 

For those asking about ISV and off throttle. If everything is working functionally, including your ISV then when you come off the gas it should go to like 1100 rpm =/- 300rpm or something and slowly come down to set idle.

BTW- a leaky IC coupler cause my car to drive fine but stall when going down to idle

 

+1. I'm curious as well!