Newbie With Intermittent 944 Turbo Fault - Please Help!!!

[denimdick]

Hi there,
I'm a newbie to these boards but I'm really hoping that you guys can help me with an intermittent problem I'm having with my recently purchsed 1990 944 Turbo.

I'll start at the beginning - about 3 weeks ago, I purchased a lovely 1990 944 Turbo with an unprecidented history file - this car has really been looked after throughout it's 25 year and 135,000 mile life. In the following fortnight the car performed faultlessly, including the 250 mile journey back from purchasing the car.

Last week after a brief visit to my parents (about 5 miles away), I started home. I'd gotten about a quarter mile down the road when I felt the car falter and shortly after the engine stalled. I managed to restart it but it was running EXTREMELY rough and wouldn't idle. The only way to keep the engine running was to keep on blipping the throttle - it was obvious that the engine was "missing" badly and there was a strong smell of petrol from the exhaust. After nursing it back to my parents I left it parked-up overnight.
I returned the following day to assess the sitaution and to my surprise, when I tried to start the car, it started and ran perfectly. I drove it around the block a number of times and decided that perhaps what had happened was somehow a "glitch". However, just to be on the safe side, I changed the DME relay, plugs, leads, distributer cap and rotor arm - I also had a new throttle position sensor fitted. (I've also bought an engine temperature switch just in case it was faulty and telling the ECU to over richen the fuel BUT I haven't fitted this as yet).

Everything was fine until yesterday. After returning home after a long Sunday blast, I pulled-up outside my house and hit the door unlock button in order to let the wife out of the car before parking-up. The instant I hit the door unlock, the engine faultered and died. Again, upon restarting the engine it wouldn't idle, ran rough and would only keep running if I kept blipping the throttle.
This morning I went to start the car expecting difficulty but you've guessed it - it started, idled and ran flawlessly! I even tried to re-create the issue by pressing the door release button but it was perfect and had no effect on the engine.
It seems that whatever is causing the issue is resolved after the engine has gone cold!
Don't make the mistake of thinking I know what I'm talking about, I'm the first to admit I'm not partucularly mechanically minded so I really need your help as I don't know where to go from here.
Do I need a mechanic or an auto-electrician?
Could it be the temperature sensor switch (I'm going to fit this when I get a little time).
Could it be the Mass Air Flow sensor?
Coil?
Bad earth?
I also have a "Scorpion Alarm" fitted - not sure how it could be this but you do hear of problems with 3rd party alarm fitments.

Thanks in anticipation guys.

[nynor]

alarm.

[soxnail]

Nynor Alarm should be a cut off and no run period ?
I think the cars operating temperature may contain a clue.
can you duplicate the issue with running the car hard (hot) then trying to use some electrical accessories ? We need to find a pattern.
Sox

[nynor]

eliminate the alarm from the equation. it is an aftermarket alarm, from what i read, and may not be as cut and dry as the factory alarm.

he stated that he hits the door unlock and things get wonky. i'd say this points to something odd with alarm.

in any case, eliminate the alarm to simplify the troubleshooting.

[soxnail]

Concur
Sox

[rick13]

Fortnight. Lol...

I'm betting temperature sensor...or temperature related..."Strong smell of petrol"

[denimdick]

Thanks for all your help.

Going to fit a new engine temperature sensor at the weekend (since I already have one) and see what happens first.

Just out of interest, can you guys to identify a "sensor" - it's just above the Throttle Position Switch with a push cap. It's just that there seems to be a lot of "play" on the spindle.

I'll try and attach a photo.

[kdjones2000]

Turbo cooling pump temperature switch.

Not related to your problem.