ACSGP

I started driving the car everyday last month, mostly in the city and idling quite a bit during jams.

The car started running rough, then would suddenly lose power and go into limp mode (won't rev part 2000 rpm). Took it to the independent, who then checked all the electrical connections, tightened them and the car ran fine again.

3 weeks later, same thing, but only intermittently. Due to the Chinese New Year holidays here, all workshops closed, and the car was not used except for a start to ensure that the battery wasn't draining.

With 2 weeks of non-use, the car is now apparently running fine, and is still in the Porsche agent's workshop. They can't seem to find any fault. The DME relay was changed before the CNY holidays, so that can't be the problem.

Seems that usage + heat must be playing a part in the problem. Any ideas?

joey bagadonuts

Cynlinder head temp sensor? Low octane fuel?

ACSGP

Thx. I use only 98 octane. May try the head temp sensor, but the Porsche shop now thinks it could be the fuel pump. Somehow I doubt it as a pump failure would cut off the supply totally, and not send the car into limp mode.

joey bagadonuts

Oil fan, thermostat, engine cooling ... all that working okay? What's the oil temperature gauge say?

Limp mode suggests your car is running really hot, right? I'm sure stop & go urban treks don't help but these cars don't usually shut down. Hmmm...

I think you're right about the fuel pump. Fuel filter, maybe?

ACSGP

The oil temp guage runs at 10 o'clock max, after the thermostat was changed when it failed. So while the car runs fairly hot, no real issues there. Oil cooler definitely works.

bwoodry

Check your coils,, i had one go bad , it caused intermittent stalling , and christmas tree effect, i.e all gauges lighting up.

joey bagadonuts

How about the engine undertray? You got rid of that, right?!

rattlsnak

have you had the air flow meter wiring update yet?

Indycam

Any codes ?
If the thing is going into limp home , it must be doing it for something its "seeing" .

ACSGP

The Porsche agents did a flash of the ECU, and no error codes came up unfortunately. But with the newer generation of cars, I feel that the mechs rely too much on electronic diagnostics, and have less feel for the car.

ACSGP

That was the first thing I thought of, but didn't have any christmas tree flashing during the limp mode. Maybe the coils are affected by heat???

springer3

These are old cars, and there has been plenty of time for condensation to build up at the bottom of the fuel tank. Intermittent problems are sometimes caused by the odd slug of water getting into the fuel system. Also, there is a strainer inside the fuel tank that can get clogged with gummy fuel and starve the fuel pump. You are in a humid climate, and I would be surprised if you did not have condensation problems.

There is a simple fuel pressure and fuel flow test described in the factory manuals. I am not sure why your shop has not done that already. It is one if the first things I would try if I had your symptoms.

Richard Curtis

Check the easy things first: Remove battery-to-ground (earth) cable and clean both ends of it. Clean the positive terminal/cable end while you're at. This cured a similar problem for me.

ACSGP

Thanks all. Have been drip feeding the info you guys supplied to the air-cooled expert at the Porsche service center. Hope that this prob is solved once and for all.

One other thought, apart from the new DME Relay, should I just change all the fuses? They must be pretty old, and this won't be very expensive (I think).

rattlsnak

fuses are either good or bad, they really dont have "wear" on them that would dictate a need to ever change them.