944 Won't run long! Need Help!

[trebor]

I just bought an 85 944 a month ago and it was running fine until 2 days ago.
I shut it off at the local store, came out and started it again, it ran fine and went about 100 feet then it quit.
If I let it sit for a minute it starts then stalls after about 15 seconds. And it will not run for any longer than 15 seconds and the idle fluctuates and runs very rough. It appears to be running rather rich as well.
So far I have checked the fuel pressure, coil, fuses, relays, the spark plugs have been changed, everything seems to be fine. The idle speed motor, mass air flow, and throttle sensor were changed shortly before I purchased the car. Also the alternator was shot, so I replaced it yesterday hoping this was the problem but such was not the case. Any suggestions on what the problem could be or what else to check?

Thanks in advance for any help,

Bob.

[Chris_924s]

FPR can cause a warm start issue- idles fine then dies?? fuel filter clogged, bad gasoline?

[SoCal Driver]

Need to do some searches on no start. Use my handle; "SoCal Driver" as part of the search. Lot's of precedures to follow. If you don't test in a certain order you are wasting time and possibly replacing good parts.

Also check out www.clarks-garage.com and www.frwilk.com for more.

[trebor]

Thank you for the replies. The problem has been tracked down to a damaged DME which was sent off to a Porsche mechanic to be tested.
Whoever owned the car before I did put in an aftermarket alarm system, and didn't wire it in properly, which ended up damaging part of the DME.

Bob

[SoCal Driver]

Originally posted by trebor
Thank you for the replies. The problem has been tracked down to a damaged DME which was sent off to a Porsche mechanic to be tested.
Whoever owned the car before I did put in an aftermarket alarm system, and didn't wire it in properly, which ended up damaging part of the DME.

Bob

Who told you this?

[trebor]

Mechanic at the Porsche dealer I had my car towed to last week.

[SoCal Driver]

Let us know when you get the repaired DME back in.

[ronin]

just so I understand, did the Porsche dealer make the diagnosis of the bad DME and then send it to another to have it tested?

[trebor]

It was tested at the one Porsche dealer. This whole problem was created because the aftermarked alarm system was not wired by a professional into the ignition and through to the DME. I will be getting it back by the end of the week and will post when I get the car running again.

Bob

[SoCal Driver]

The reason "we" are highly suspicious is that there is hardly any way you can damage a DME from the outside. Not to say that it wasn't.

Also it's an air flow sensor not a MAS -- not a heated element just a mechanical flap and resistor. The double contacts can be repositioned on the carbon coated ceramic resistor giving new life to a worn unit.

It's a throttle switch. Contacts at both ends of the throttle travel. At idle the switch shuts off the injectors till the rpm's drop to 900. This sometimes over shoots and you get the notorious stumble as the engine tries to catch itself and come back up to 900 rpm idle. The WOT side of the switch disengages the O2 sensor.

You must have got a good deal on it if the PO couldn't figure out what was broken.