Luis de Prat

OK, I've about had it with this recurring problem.

The 944S2 keeps doing this out of nowhere. Yesterday it started stumbling and we had to drive back to the garage at like 7 mph, pressing the "pedal to the metal" with very little go.

So far, I've replaced a lot of items, including the following:

Ignition control module
Spark plugs
Idle Stabilizer Valve
Throttle Position Sensor
Airflow Meter (with brand new unit)
etc.

I'm suspecting either DME relay or Fuel Pressure Regulator. Maybe the rotor?

Your ideas are appreciated. I'm beginning to get discouraged with this problem. TIA

RMills944

Fuel pressure regulator?

Mark944na86

hi Luis,

Sorry to hear this has raised its ugly head again.

My understanding is that the DME relay is usually a go-no go thing, but I could be wrong. At any rate, since they're not expensive and are useful things to have in the glovebox anyway in case one does go on you, it seems like reasonable thing to try.

If I were you, I'd probably be replacing things in order of cheapest to dearest, with regular maintenance items like rotors, etc. getting priority. On the principle that you'd be buying these things a little further down the track anyway.

Don't be too discouraged! After all, you live in one of the world's most beautiful cities, you have one of the world's most beautiful cars, summer's on its way, and so what's a little thing like this in the bigger picture!

Take care,

-Mark

gruntie

Don't know if you've already checked, but I've twice had problems caused by a faulty temperature sensor on the S2:

First occasion, intermittent rough running & almost total power loss at cruising speed which would clear up as suddenly as it appeared. Apparently sensor was telling the DME the engine was stone cold & thus drowning in oversupply of fuel.

Second occasion, with replacement sensor, either a) engine would start from cold, run for 5 secs, & then die & could not be restarted, or b) idle would suddenly hunt up & down from 800 to 1800 rpm. Both problems intermittent and drove me mad. Needlless to say whenever I could get it checked it always behaved faultlessly.

Hope it helps, at least it's cheap & easy to replace.

Riff

Luis-

Sorry to hear this. Are you sure the car is getting the right amount of fuel? Perhaps a weak fuel pump or perhaps a clog @ the fuel filter?? Just throwing additional ideas out there.

Good Luck,

Luis de Prat

Thanks fellas. Riff, the fuel filter was replaced also!

Temperature sensor? That's a new one!

pikey7

is there no specialist there to bung a diagnostics tool on?

Tom R.

does the S2 have fusible links? I had a similar problem in a 280Z and it was the fusible links. when they would heat up the car wouldnt get enough power, when they cooled all was fine. total cost about $3.

Crank sensors, in the oldsmobile they were not an on/off problem. we often got some stumbling/fishing for the right combo.

How old are the wires? may be similar to fusible link problem, they look good, but the metal inside is acting funky.

I posted a similar problem on the 928 board and asked a porsche mechanic at a DE, he said try the crank sensors, then the lambda which is the fuel injection computer, guys on the 928 board said to send the computer out to be re soldered, like our cruise control computer.
https://rennlist.com/forums/928-forum/200363-may-get-a-deal-on-a-928-how-high-to-i-go.html

jonnybgood

I had a bad temperature sensor and my car ran ok. It was just too rich. I did not experience what you describe or what gruntie mentions. Of course I have an S and not an S2. Check your spark plugs to see if they indicate a rich mixture to rule this out.

My first idea is along with what Tom is saying. I have read of the ground connections in the wiring harness going bad and causing problems. It seems like you are loosing one of your signals to the DME. It could be at the soldered connection in the DME as well. I recently resoldered my DME connections just as a maintenance proceedure, can't say it cured anything.

greg rx2

guys it must be the time i have the same problem with my 944 turbo s. starts up fine, idles fine, when cold the car runs like new. once the temp needle gets to the first mark the car will not go above 1400 rpms. then it magically fix itself and will run fine then at a stop sign same thing, or just going down the road you will feel the engine miss,lose power then clear itself. i have replaced fuel filter, checked fuel pressure at the fuel rail with gauge good,replaced air flow meter ( not new but known good),pull plugs to see if its running rich, not it,. i have emailing markus blaszak he has been telling me what to do but so far nothing. i feel your pain.
greg

ernestedward

Luis - my S2 is in the shop right now for what sounds like exactly the same problem... I'll let you know what they find (if anything).

944_S_TYPE

Hi On my "S" I had a couple injectors that would fail one second then be fine the next. Try www.944online.com. They have rebuilt cleaned, pressure tested injectors for the "S" for around 50.00-60.00 each.

To see if you have a dead injector start the car, Start pulling plug wires, When you find one that makes no change that is the dead cylinder(S)

BNTS

try the oxygen/lambda sensor, I had similar problems with my BMW and a new O2 sensor fixed it.
It idled Ok, but no power at all on other loads.

/Niclas

Luis de Prat

Thanks for all the replies.

Tom: the reference sensor could be it, but there's only one on the S2. Not sure what you are referring to by "fusible links."

Niclas, the car has a new oxygen sensor from the Porsche dealer.

Ernestedward, last time I had something sporadic like this it was the Ignition Control Module. In my case I can't imagine it going bad again in just 3 years, though. Could be your problem if you haven't replaced it. It's specific to the 944S2. I'll be looking for your report!

I'm replacing the fuel pressure regulator and damper today or tomorrow to see if that helps at all. I bought the parts before replacing the TPS...

Bret 944

I had a similar experience as gruntie on the '84, it was the temperature sensor. Cost about $30. The damn thing wouldn't go anywhere even with the pedal to the floor. Also ran really rich when it ran crappy, you could smell it and see black smoke out the back at idle.