Van

This is a turbo, but the idea is the same:

David McLean

Okay, replaced the electrics part of ignition switch. Dme relay installed, no jump. Car starts first turn BUT to a stumbling hunting idle until stall. Will not accept any accelerator whatsoever. Replaced vacuum lines. Found a pool of warm gas/petrol on the engine block just where temp sensor is and below throttle body. Where could this leak come from and is it related to my issues? Thanks Guys

JacRyann

Pool of petrol could be from cracked fuel-hose elbow from rail to dampener. Check that carefully with engine-running to see if you can find the drips. Replace that IMMEDIATELY or else you'll have engine fire.

Rough running by be related, but most likely vacuum leak. Which are typically in the larger J-boot and/or brake-boost or idle-stabilizer hoses. You way to detect leak is to measure vacuum levels in the intake-manifold. Should be around 20-in.Hg. with warmed up engine. Leak will cause lower-vacuum and mess with your fuel because the FPR is linked to vacuum. Also vacuum-leak will cause AFM to send erroneous readings to the DME. So.. do these two things and you'll narrow down your problem:

1. measure AFM output-voltage at DME-connector @ idle with warmed-up engine
2. measure intake-manifold vacuum @ idle with warmed-up engine.

David McLean

Thanks for this @jacryann, have gone away for a week Christmas break, but what you say about the leak at the elbow to the dampener makes sense. I will get onto this in a week

V2Rocket

Your fuel injectors may not be seated all the way as well, that would let plenty of gas out and air in.

David McLean

Okay, back from Christmas break and got stuck into 944 that had stumbling idle and would stall eventually and would stall when applying any accelerator. The car is now running perfectly. Main issue turned out to be damaged knock sensor (speed sensor). This was aided and abetted by numerous vacuum leaks and poor fuel pressure. I replaced sensor, replaced all vacuum lines including "J" hose, new clamps, new fuel pump, new distributor cap and rotor. Thanks to all for the help and suggestions. Will continue with the restoration and will make some fresh posts in due course. Cheers

Legoland951

You did not mention how the gas leak was resolved. The fuel hose elbow from rail to dampener had a USDOT recall and is infamous for starting fires in the 944. I have personally bought over 10 burnt 944s and parted them. This is no joke. Porsche USA had a "secret" free replacement but you have to tell them about the recall. They will check the VIN and they will provide parts and labor for free (at least in the past). The gas leaks from the hose directly to the plug wires and if they are not in very good condition (arcing intermittently), it makes for a perfect igniter for the gas.

In the 90s, I drove to an intersection and saw a very nice 944 turbo stopped at the sign. It started to smoke and caught on fire right in front of me. I called 911 from my cell phone (when cell phones first came out with the "brick phone") and by the time the fire truck got there, the fire had destroyed the car and melted the front wheels enough to wrap around the calipers/rotors. A semi truck driver came out with a fire extinguisher at the start of the fire but burnt his fingers trying to unlatch the hood and open it.

It is no joke.

David McLean

All of the above things discovered assisted in the car not running - BUT, I have now discovered the BIG problem. I changed the battery and got the wrong one. Result is that the positive terminal of the battery shorted out on the bottom of the hood. RESULT = fried DME and ALTERNATOR. Had the alternator rebuilt and put in a new DME and (together with all the other things I have done) she is singing like a canary!