Adam944S2

Hi All,

I have a 1990 UK spec 944 S2. I have a problem whereby the engine just dies while driving along. When this happens I pull over and take it out of gear and take my foot of the gas. Sometimes the engine will die completely, but will restart and sometimes its sits at around 800 rpm and runs unevenly. When you try to rev, it goes up to about 2000 rpm, but won't go any higher, behaving as if someone were removing the high tension lead or some other ignition component. If you keep pumping the gas pedal it will eventually creep past 2000 rpm and all of a sudden will rev freely and I can engage a gear and drive away without a problem untill it happens again. I've looked for some sort of common ground as to when this happens and the only thing I've noticed is it tends to behave like this moreso when the weather is hot. It also behaves like this wether the engine is hot or stone cold.

I posted here a couple of weeks ago and someone suggested the DME relay. I changed the relay and thought I had cured the problem, then the next day it happened again.

Any help would be much appreciated.

Adam

pete944

It sounds like a fuel problem.
Check the fuel pressure regulator, fuel filter, and fuel pump.

Dal Heger

Sounds electronic. Look at the AFM or the throttle position sensor. One of the sensors is giving wrong information.

Dal.

pete944

If pumping the gas pedal keeps it running wouldn't it be fuel related? I would think with an electrical problem it would be either on or off and giving it gas wouldn't make a difference.

944S2NUT

These S2 issues are turning into an epidemic.

Dal Heger

No, the gas pedal isn't connected to the fuel system in any way. All it controls is the throttle. The air flow meter tells the DME how much air is being sucked into the system and then the DME controls how much fuel is squirted into the engine via the fuel injectors.

Sounds like the AFM has a bad spot in the carbon tracks that read how far the barn door (air flow meter flapper) is open. Chances are that opening and closing the throttle moved the flapper a few times and it cleared the bad reading. Basically the AFM is worn.

The thottle position sensor is the same way, a metal wiper that tracks on a carbon track to vary the resistence value that the DME sees - thereby "seeing" how open the throttle is.

The fuel system is really robust, not much can go wrong with it.

The S2's are getting to the age where parts wear out, it happens.

Dal.

Adam944S2

Guys,
Thanks for all the suggestions, they all seem plausable. Can anyone tell me what is the "AFM" and where is the throttle sensor located?

Thanks again

Adam

Jim @ EuroWerks

Ya know, I once had a rotor button bite me like that. It idled perfect as soon as you press the gas it would cut off. turns out there was a burnt spot in the rotor. The easy way to find this would be remove dist cap. Place a spark plug in the coil wire and (INSULATED) hold it up to the rotor. If the spark jumps to the rotor,when spinning the motor over, the rotor is bad. You see the rotor is not grounded. Therefore the spark should go around it to ground not to it.

Dal Heger

The AFM (air flow meter) is the big silver box right at the front of the engine, connected to the rubber boot that goes to the intake (through the throttle body). The TPS (throttle position sensor) is the little black box connected to the throttle, usually the other side of the throttle linkage. Both have wire harness connections on them that you can take off by wigglilng them off, they snap back on.

Dal.

Adam944S2

Thanks Dal

Adam

Roy LaZelle

Sounds like the electric (electronic ?) idle control valve to me. I had similar problem to yours last winter. I took the valve / motor off and cleaned it out with carb cleaner. I did test with 12 volts from the battery to make sure it would move in both directions before I put it back in. It has worked fine since then. My only annoyance doing the repair was the single use hose clamps that it was attached with. --Roy--

Adam944S2

I'll check it out.

Where is it located?

Thanks in advance

Adam

Jim @ EuroWerks

If all this stuff doesn't help, ck to see if you have something loose in the catalyst. Sometime blocking sometimes not. Also I've seen the fuel pickup strainer come loose in the tank. It will float around sometimes blocking the fuel sometimes not.