TR6

I need some insight into a stalling issue. I've had the car for a few weeks and I've noticed since I've had it that when I come to a stop and push in the clutch, the idle will drop to almost stalling before bouncing back to normal idle. I thought perhaps this is normal. But this is the first time its actually stalled. I was creeping along in bumper to bumper stop and go evening traffic (about 100 degrees F outside). Its one of those situations where you move forward only a couple of car lengths at a time while continously engaging and disengaging the clutch, inching along in first gear. I had the Air conditioning on (as I do every day in traffic), but today it stalled when I pushed in the clutch pedal as I came to a stop. The idle just dropped to zero and didn't bounce back. Then it did it a second time a couple of minutes later. After that I turned the AC off for a while. As far as I know, the car doesn't have a light weight flywheel (although I cannot say 100% for sure). What could be causing this?

hawk911

I have the same issue, and also can't swear there isn't a lightweight flywheel in the car. I don't believe it to be chipped either.

nekbet

Find another C2 and drive it/rev it... You'll know if you have a LWFW..

I'm assuming you mean C2 and not the RS in your sig, right?

-Mike
1990 964 C4 Targa

TR6

Correct. Its an RS America, but a standard C2 engine.

dfinnegan

Try doing an adaptation with a Hammer or the free software found here on Rennlist.

Also try cleaning the ISV valve and the intake manifolds.

Cheers,
Dave

elliottc

I had a same/similiar issue. It was the idle stabilizer.

911URGE

Overnight mine started this behavior where the idle would drop to low and stall. Also had a bit of wandering idle. I cleaned out the Idle Control Valve and MAF unit with carb cleaner. Got lots of black soot out. I also tested & cleaned the idle & WOT switches and cleaned up the caps/rotors (time for new ones). It now idles so much smoother and it does not drop to low or stall when letting off the clutch. My wife drove it yesterday and even she notices the difference.

TR6

Where is the idle control valve (and is this the same thing as the ISV) and what is preferred method of cleaning it?

Is the idle stabilizer different than the ISV or idle control valve? Did it have to be replaced of cleaned? Forgive the ignorant questions, but I have just begun to learn about these cars. -thanks

C4Russ

Just to add my .02

My car doesn't really like easy driving or loafing along. If I do a tad too much city driving without the benefit of taking the car to redline a few times, the car can start to run less well. I don't want to say it runs poorly and I can't find anything that needs repair or replacement. However if I notice the car is not running like I'd expect or that it stalls, I take it for a spirited drive with several runs to redline. After that, it runs like one would expect.

Conclusion: Drive it hard.

hawk911

The ISV is the idle Stabilization valve, and it's on top of the engine by the throttle control. It's a silver colored can that has an extention on each side. Do a search on ISV, only cuz I'm too lazy to do one for you.

TR6

Trust me, it gets pushed to redline each time it goes out. I don't baby it.

PorscheZen

Try this link at bottom for ICV valve pic.
Good luck
https://rennlist.com/forums/964-forum/288883-inconsistent-idle-after-tune-up.html

Pingo

Second that, same problem same solution for my car!

911URGE

It is the same - goes by ICV or ISV. Go for the cleaning of the ICV with a spray carburator cleaner or Throttle Body Cleaner. Spray it right into the unit - then shake it, swirl it, jiggle it, pour it out and do it again until no more black stuff runs out and let dry completely. Mine took nearly half a can. Also, dont mess with the ICV at all - dont stick anything in it like Q-tips. There is nothing to adjust. Also, just because its clean does not mean its not broken. You could have the cleanest broken ICV in town.

The AFM (Air Flow Meter) is just as easy and straight forward to clean.

If you have not already purchased Adrian Streathers book on the 964 - Do so, its a MUST have.

surfdog4

Reviving an old thread here, but I was chasing down the same issue of the idle dropping rapidly when you push the clutch in....i know i do have a lightweight flywheel, and i was all set to accept that fact until i started reading about the ISV...my only thought though is that I don't have idle problems others seem to claim with an ISV problem. So might my issue just be the lightweight flywheel?