Idles rough and drives jumpy when cold

[1.2gees]

I would appreciate any ideas as what might be wrong with my car, when I turn it on the first thing in the morning, my car runs rough, and idles at 900, meaning the idle does not increase. In fact, now that I think about it, I don't remember my 944 idling at a different speed than this, EVER! Also before the car is driven 1-2 miles there is a slight jumpiness to it, though I'm not sure somebody else would be able to feel this. There is no lack of power. Anybody have any ideas?

[NvrFstNF]

I had an 86 that did something similar. The car idled rought until it warmed up. I believe the problem may have been a leaking head gasket that allowed a small about of water into one or more of the combustion chambers. After the water evaporated the car ran smooth. This is just one idea. I it might be a good idea to put a small amount of radiator stop leak in as a preventative measure.

[p0r2chby]

Have you considered the posibility of a vacuum leak

IMOP, the use of "radiator stop leak", particularly the fine powder type, is the quickest way possible to kill a 944 water pump

[Pilot_951S]

1.2gees,

Vaccum leak sounds plausible.

Have you considered the possibility of a failing, but not totally worn out engine mount.

Also what about the fuel filter? When was it last replaced?

Worn distributor?, Plug wire arcing?

More shots in the dark, you didn't specify much.

[Pilot_951S]

I'm thinking about sometihng to do with the cold run mode, DME maybe, or sometihng. I'm out of my expertise on my theory but it is an idea.

[1.2gees]

I've got all new vacuum hoses, connections, for some reason I don't trust them, but they're new. The only thing I don't have new is the distributor in the ignition department, everything else, including a high output coil from jacobs, 8.5 wires and so on are upgraded and maintained. My engine mounts are almost new as well, I don't suspect them because when the engine is warm, drives beautiful, idles fine, but when cold surges, idles slightly rough, I'm sure somebody else wouldn't notice it easily, also motor mounts wont make the car less drivable either. I'm guessing a DME going bad or idle stabilizer, the auxilary air regulator or something like that, hopefully cheap. I was hoping there was a common part that goes bad, and as soon as I posted this somebody would scream out yes, that's what happened to my car, .... is what you need. No such luck. By the way car has new head gasket, and very strong running engine, the fuel filter has been replaced twice in the last year by yours truly, and this problem has been a lot more easier in colder days, first thing in the morning, has been doing it since I bought the car, almost 2 years now... Thanks for the help so far, any other ideas/suggestions welcome.

[Doug M]

My 85-944 acts the same way. I checked the eng. temp sensor which activates the cold run circuit and puts the O2 sensor in service when the the eng. is warm , it was ok. It seems to be running lean when cold which makes it run rough. My O2 sens. doesnt seem to read correct but I havnt found the spacs. yet. I guess I will check the cold start valves next , they look hard to get to.

[1.2gees]

Let me know what you find...
Ahmet