Carpokes Porsche Forum

x posting this anywhere I can think of for some help - I'm desperate!

Hi all - having a major problem with my 944S after getting it back from the mechanic. Of course it's the weekend, so I'm troubleshooting myself now.

Brought the car in to a majorly reputable shop here in the NY area to have a few things looked at that I couldn't figure myself. Car idled fine when I brought it in, with the occasional stumble/surge that always seemed to work itself out.
At 115k miles, I had a feeling the ICV should be cleaned / replaced at some point but never wanted to touch the intake manifold myself.

Shop removed, cleaned and replaced the ICV, stating it was totally frozen when they took it off the car. They freed it up, put everything back together and "adjusted the idle" so the car ran at 1100RPM at idle.
On my drive home I noticed a few things - the car was a little odd to drive, it never really seemed to actually be "throttle off", and had a few stumbles where it'd idle at 500 - VERY low.

Once home, I checked the throttle to see whether the TPS was being contacted at idle. It wasn't.
I can hear this audibly, meaning they adjusted the screw that forces the throttle open/closed. Not something you're supposed to do on the 16V cars, and would explain why the car was driving odd.

I tried adjusting the screw so that the TPS was contacted when idle, but when seemingly correctly adjusted (just BARELY making the switch, but hearing the click when the throttle is closed, and open just off idle throttle), the car won't idle right. It drops down to 500, and dies. I can manually hold the idle up with throttle, but that's obviously not smart.

I'd LOVE to get the car on the road this weekend for Father's Day. It will be going back to the shop Monday, but it's a huge disappointment.

My guesses are either that there's a big vac leak somewhere after pulling the manifold, or the ICV has finally bit the dust.

This was a notable shop that other members use, I guess they're just not as knowledgeable about the 16V cars.

Any insight is appreciated.

Update: with the ICV unplugged, and the TPS switch made, the car runs - albeit idles high at 1100-1200RPM.

Adjust the throttle stop screw so that it just contacts the throttle lever without really opening it at all. It is there to prevent the butterfly from scoring up the throttle bore and getting hung up. Then disconnect your battery for a minute or two to clear the DME's memory. Re-connect the battery and start the car. It may run a bit rough, but should stay running. Go gently drive the car to warm it up. Once it's up to temp, park somewhere and let it idle for 5 minutes. Don't touch the throttle while this is going on. Also make sure any big electrical load (lights, fan, defroster grid, etc) is off, as well as the AC. During this time the DME will "re-learn" the correct idle mixture and idle speed. It will be fine after that.

BTW, don't expect your tach to be all that accurate - but the DME will set the idle speed to about 840 rpm.

appreciate the insight. yeah i had re adjusted that stopper and tried that, seems the ISV might be shot. the second i plug it in, the car quits. the shop said it was pretty seized up when they pulled it out

An update here:

mechanic ruled out every other option and then compared the ISV to another one off a 964 he had apart (same part) and discovered that while mine moves, it's not fully opening / closing meaning the valve is kaput.