markrcarter

After about 1/2 mile of driving my 944 turbo engine cuts out. Will eventually re-start but re-occurs until engine is warmed up. May be related to wet / cold weather but not entirely consistent.

Any thoughts would be appreciated before I spend ££ getting it diagnosed (or not!) by a specialist.

mark

Tom M'Guinn

Do you have spark when the car cuts out? If not, check the DME relay. If so, might want to check the temp sensor in the block.

Dal Heger

Replace the DME relay, it's the cheapest way to diagnose, and even if it doesn't fix it, then you can rule that very common item out.

Dal.

markrcarter

Thanks for your help,

I changed the DME relay but no difference, the AFM and engine temp sensor output OK when tested with multimeter. As the engine re-starts almost straight away I have not managed to check for a spark after it dies.

The problem is totally repeatable when the engine is cold. It cuts out twice (always) in the first couple of miles and then does not miss a beat. I can deliberately stop and start the engine to prevent it cutting out.

Current thinking is that its an ECU fault such as dry joint, water ingress etc but any other ideas appreciated

Mark

Eyal 951

some ideas, mostly geuss though:
Idle Stabalizer Valve
coil
ECU (maybe O2 censor related?)

Dal Heger

The next option is a broken solder joint in the DME. When it's cold and started, thump on the front portion of the passenger side floorboard with your fist, hit it hard, if it dies, then you know you have a broken solder joint in the DME. The DME is behind the footwell wall on the passenger side.

Dal.

Rip It

why would it do this twice and then not miss a beat ? I would unplug the tps and see what happens, its free and its easy to do...unplug it.

Bri Bro

Might have a temp sender/connection (one going to the DME) that is bad. If it didn't tell the DME that the engine is cold, the mixture would be lean until the car warmed up.

markrcarter

Good news and bad,

The good news is that when i thumped the passanger side footwell, sure enough the engine died suggesting a DME fault
The bad news is that the car refused to start after that!

I opened up the computer and found a resistor hanging on by one end only. There was a lot of brown residue around it suggesting it had fried. I soldered it back in place but no joy - car still won't start. There is no spark and I can't hear the fuel pump running when an assistant turns the engine over.

There is a 9v input to the DME when cranking and the speed sensor checks out OK with a multimeter (based on clarks garage tests, www.clarks-garage.com). Therefore i suspect the computer is dead. Anything else I can do before i spend $$$ ?

blodstrupmoen

It would probably be a good idea to find out why, before instaling a new DME..

Dal Heger

Take it to an electronics repair shop and have them replace that resistor. Also have them check all of the other solder joints. Usually there are a few that crack/fail with age and vibration.

If the DME is truly destroyed then you can get one on ebay for not too much money, but I'd take it to an electronics repair shop first.

Good luck.

Dal.

markrcarter

Have eventually got this sorted. DME was bad (more than just a dry joint) so I got it re-conditioned. Car fired up first time when re-fitted and has not cut out since. Was more expensive than a 2nd hand unit but at leat I know it works OK and have a 12 month warranty

Mark