Porsche Enthusiasts Club Forum

Hi
I have a problem with my 1990 944 S2 3.0
Initially the engine would completely cut out whilst I was driving. It would then bump start up again (as I was still rolling forward and in gear). If I stopped the car it would start up again and run for a while before cutting out again.
I replaced the fuel filter, DME relay and the 2 ignition relays, fitted new plug leads and cleaned up the DME earth.
I took the car out for a 20 mile run and appeared to have fixed the problem of the engine cutting out.
I parked the car up for the day but when I went back it was difficult to start, when it did start the idle was very rough and I had to rev the engine to get it to run properly. The idle also seemed to “hunt” between about 600 and 900 RPM.
I have checked the Alternator voltage regulator, it’s giving me 13.9 volts at idle and 14.0 volts at 2000 RPM so I think it’s OK.
I recently fitted a new coil along with a new distributor cap and rotor.
I’m not sure what to try next.
Has anyone seen a similar problem or have any suggestions as to what is wrong?

Spark Plugs?
Air Filter?
One thing that was pointed out to me is the AFM - check the wiring harness connector and the connection pins within the plug for this
What is your fuel pressure like?
DME temp sensor?
Engine earth lead?
Battery earth lead?
Vacuum leak?

EDIT: Could also be the idle stabilizer valve if it is hunting...

Idle Control Valve

Stuck?

I had similar problems eventually changed crank sensor after same happened on my 993. Bad or no hot start then died after warmed up. Then battery earth strap failed.The non return valve on the fuel pump had also failed. But it does sound like ISV in your case.

Thanks for the suggestions guys.
I forgot to say that I changed the air filter and the plugs when I fitted the new coil and dizzy cap.
I'll start with the earths and the AFM connections then see if there's any vacuum leak.
I could do with a fuel pressure gauge so I'll put one on my shopping list and check that next.
After that I'll try the new bits, Idle stabiliser valve, Temp sensor and crank sensor in that order.

Cheers
Neil

Temp sensor is dead is easy to test just stick a multimeter (set to ohms) on it when the engine is cold and when it is up to temperature and compare the readings to the factory manual (figures here on clarks garage)

http://www.clarks-garage.com/shop-manual/elect-19.htm

There are several guides out there on rennlist (perhaps here) on cleaning the ISV.

The price of a idle control valve will make your eyes water,

I would remove it, fill it with carb cleaned, and let it soak for a while then blast it out again

Then with a battery test the thing
Center is common the other two connections are live just touch and make sure it turns both ways and reassemble

I had a new (well replacement from a scrapper) motor fitted to the S2 soon after I got it and it's ISV was completly stuck. Wouldn't idle bad starting and only ran on open throttle. ndie started playing with the AFM which shocked me a bit" It's the ISV" I said so removed it from my old motor and swapped it, bit fidly but it worked and then I had to send the cocked up AFM off to be recalibrated.
As Waylander said, remove it and give a good clean do not let fluid get in the electrics. 993 one here it's identical and just as akward to remove.
http://www.jackals-forge.com/lotus/993/993_60k_isv.html

It did, but I've found a second hand one which I should get next week, I'll check that it works before I fit it.