TRDRacer

So my engine still turns over when I turn the car off. I think it is carbon buildup on the valves, so i think that the carbone is still hot when i turn the car off, so when the valves hit down again after I turn the car off they egnite to turn the engine once more!

So my question is what is a good cleaner to use to get that carbone desolved?

Thanks!

PXJ800

Is it just one chug after you kill the ignition? It sounds like a unique problem. Have you visibly checked the valves?

white924s

so the car keeps running after you turn it off? does it die on its own?

if it doesn't die on its own, I'd look at the relays and ignition switch. If it does, does it run ok when the key is on? I would hazard a guess that you might have leaky injectors rather than burning carbon buildup. If the carbon buildup on the valves (or, really, anyhting else on the valves themselves) was igniting, you wouldn't hear the engine turn over, but rather you would hear one (or more) pretty distinctive back or front fires (you would also hear these while the engine is running). A leaky injector, however, could lead to small amounts of fuel dribbling in after shutdown and combusting at the top of the power stroke (ie when cylinder is roughly at peak pressure). Thus, it would be the pressure of the piston compressing the fuel/air mixture that would set it off, much like what happens if you have detonation or knock, and the mixture would presumably be very lean, so pre-ignition would not be surprising.

In addition, injector o-rings are items that wear out over time, so I would suggest that you start your search there. Hope that helps

Yabo

Mine diesels a little after shutting off every once in a while if I don't let it setlle for at least ten seconds or so , sometimes. Dunno why, been doing it since I got it and after the rebuild it still did so i'm not worrying about it. May not be your problem though.

Ben951S

Mine does that too, but only if I go to 'full off' or just the 'first click' off. If I go to one from 'full off' it typically shuts down correctly. I thought it was my ignition switch, as I didn't want to 'test it' by turning it to the problem positions and having it fire once or twice more... =(

GMS

If it's a 85/2 and newer, replace the turn signal relay with the latest Porsche part number part.
There was an problem, and a subsequent TSB, on "dieseling" of the later model 944.

TRDRacer

Ya my engine is old and never been properly serviced but I am getting around to fixing things slowly! My engine after turning off just loops again till it completes the cycle! My mechanic told me it was carbon buildup and he showed me an engine with it and said it was doing it aswell for the other owner! But the Injectors sound like that might be the next thing i am going to switch with the seals!

Also GMS, what does the turn signal relay have to do with the engine looping again after turn off?

GMS

Again, this only applies to 85/2 and newer 944 models. There was a problem with an electrical back-feed which kept the engine running after it was switched off. It's the same symptom as "dieseling" but a different cause.

TRDRacer

Do you have a part number? and Price or vender to buy from?

GMS

Again, as a reminder, this is only for the 1985/2 and onwards 944 models.

The current part number is 1HO 953 227A

Previous number was 191 953 227A and the original number was 111 953 227D. Check the part number of the one installed.
Any parts supplier can get one, probably about $20.00.

If you want to test, remove the relay and drive the car in the same way that causes the problem you are experiencing. If the fault goes away, it helps tracing the cure.