A quick update on my fathers 944s, had major problems starting it. Removed inlet manifold, blanking plug glued back in, tdc sensor replaced, injectors serviced, knock sensors replaced, temperature sensor replaced. Engine re-assembled, still wouldn't start. Checked fuel, ok, checked spark, ok. Finally checked firing order, completely wrong, AA man had completely mixed order. Put it correct, turned key engine started. One remaining fault, intermittent misfire, no common cause, idling, cold hot etc. I think it is an intermittent electrical fault. Any clues.

Thanks

Foz

 

Since it is an S, there is a sensor that likes to short on the power steering pump, which in turn fries the wires back into the wiring harness, and can damage the injector wires (been there, done that), so it could be due to a short in the wiring, which really is interesting since you said the injectors were firing out of order....I would listen to each injector specifically with a stethoscope to see if they are all firing continuously. Each should make a click when it fires.

 

Can you give us a bit more info on the "intermittent misfire". Random occurance, no consistent pattern to it, right? Is it an engine miss, like you are running on three cylinders for a moment and then it runs fine? Or is it more like a hard knock for a moment? Does the idle dip when it happens? Gimme details.

Regards,

 

The misfire is intermittent, the engine may start on 4 cylinders, it may start on 3, the idle drops,the engine does not idle smoothly, if you rev it, you can hear it is only on 3 cylinders, then it will clear and run on all 4. I have heard it could be down to the head gasket between 2 and 3, however, I don't think it is due to the unpredictable nature, and the intermittent nature. I hope this is a bit more info, I look forward to some clues.

foz

 

How did you fix the firing order problem?

 

I am gathering from his first post that the spark plug wires were in the wrong order.

How old are the spark plug wires? Can you tell which cylinder isn't firing, and is it always the same cylinder? We'll assume for the time being that the injectors are fine, since they were just serviced. How old is the FPR?

Regards,

 

plug misfiring or old sparkplug wires.

 

I recently helped a guy with a 944S troubleshoot a very similar problem. He wound up with two issues. First, his coil was deteriorating, replacing that helped a bunch, but didn't completely solve the problem. We were able to determine that the ignition control module thats located in the area behind the drivers side headlight (its mounted on a heat sink, pretty obvious once you look under the hood) was faulty.

HTH

Regards,