Porsche Enthusiasts Club Forum

Hi all. Returned to 944 ownership after a break of a few years with a tidy Turbo S. She has been well maintained and drives nicely with no untoward rattles, squeaks or leaks. However, when she is cold it takes an age (well 2-3 seconds) for the revs to settle back to idle. This happens if you blip the throttle just sat in the car or when driving. It's particularly annoying when changing gear as the revs never really drop to idle on a gear change. When the engine warms up it drops back to idle immediately as you would expect. I've searched around on the internet but not really had any joy finding anything on this subject. Any help would be appreciated.

It could be the TPS (Throttle Position Switch) which has a plug running to it,it is positioned opposite the throttle body operating cam,does it have a faint click when you operate the throttle manually from under the bonnet it should click when first opened and closed, adjustment is possible by 2 x 4mm screwbeing loosened (awkward) it may also require the idle screw tweaked which is placed on top of the throttle body, is the throttle returning to closed unobstructed ?

BTW the Porsche 944 Turbo S was only made for MY 88 in very limited numbers in the UK only 40 odd left , your car will probably be an SE.

Hope this helps out.

The following will cause a slow return to idle.

Throttle position switch having a bad idle contact within it.
Throttle position switch not being correctly adjusted
Idle adaption not being set (involves inserting a jumper wire into a diag plug under the bonnet and adjusting the idle screw)
Vacuum leak (any of the small bore vacuum hoses not being connected)
Bypass valve having a bad diaphragm (vacuum leak)

Thanks for the quick replies. I'll check the TPS, idle etc at the weekend and report back. It is indeed a SE, I was being a bit lazy in typing

As Jon has commented on this thread, I hope no one consider me too rude by asking about my own possibly related problem.

My idle speed falls away very quickly when the car is warm, hitting about 400rpm and causing the car to virtually cut out, and frequently for the low oil pressure tell tale lamp to briefly illuminate.

What is this likely to be caused by, please?

Managed to check things last night and adjust the idle jumping the connectors in the diag socket. Idle now stable. I had the engine running while making the jumper wire to keep it up to temperature and noticed that the revs kept varying. Gave the Idle Control Valve a tap with a screwdriver handle and they settled down. Guess a new ICV is on the cards. This is probably the cause of my problems. TPS etc were all ok and couldn't find any vacuum leaks.

My money on a vac leak Simon. Check all the vac lines you can see. Mine done that when then line blew off the one way valve next to bulkhead with the blue bit on it.

Stuart

Had hoped that I wouldn't suffer as I have all new vac pipe. (

Funnily enough, I wanted to ask the same as Simon, but mine is an S.

Generally mine is a cold idle issue, runs fine if the throttle isnheld steady but as soon as you close the throttle the revs drop to 400rpm and almost stalls. It was even doing it in traffic yesterday.

Am I right in thinking that the 16v models need the idle adaptation setting with a diagnostic tool such as the Bosch Hammer? I will be whipping the inlet off and checking for vac leaks, but wonder about plugging it in.