Porsche Enthusiasts Club Forum

Hi all,
I have an intermittant starting problem on my S2 which has recently been serviced by an OPC. Occasionally when either hot or cold (usually hot) the engine will turn over as normal, fire, and then immediately stop. It is as if it is only firing on one cylinder. This can happen 10 or 15 times and then just when I have given up it starts and runs as normal. I have replaced the DME with no effect and am at a loss what to check next.
Any ideas?

Steve

When I had a similar problem it was the plug on the side of the MAF - or whatever you call it. It just needed cleaning and I've never had any problems since.

Thanks John,

Could you please explain what the MAF is ?
Thanks

Steve

Didn't think S2s had a MAF (Mass Airflow Sensor)?

If it's the same as the lux it's an AFM (airflow meter). This is really just a pot attached to a door which is opened and by the airflow.


Adam

See, I knew I had the wrong name for it. Whatever it's called it's a grey metal thing at the front right side of the engine bay, the top looks like a waffle iron. On the left of the unit is a rubber covered plug. This is the plug I took off, cleaned, refitted, and it stopped the problem.

Worth a try.

This sort of problem assuming the ignition system is 100% is either Air flow meter (AFM) or throttle position switch (TPS).

Thanks Jim, Are these items that can easily be replaced? or do I need to book it into an OPC to get the work done?
Regards

Steve

Both easy to change, AFM has a 4 fiddly 10mm headed bolts in the air box but plug & play really, around 30 minutes top. The TPS will need setting up after being moved but this is 2 minutes work & covered in the manual.

Thanks Jim, much appreciated.

Steve

Hi again,

This problem has now entered a new phaze!! I replaced the rotor arm and distributor cap before investigating the throttle sensor and mass airflow meter, but only a small improvement. The airflow meter is over £600 exchange from OPC!

The situation now is: when starting from cold the engine turns over but will not start until I stop cranking and retry when it fires straight away, when running it runs beautifully. When the engine is warm starting is normal. The big worry is there is now a strong smell of petrol when the car is running, particularly when the engine has stopped. I can find no leaks of any sort and don't know if it is connected with the starting problem.

Any more ideas anyone?

Thanks

Steve

OK what it sounds like is happening is that you are not getting a prime from the fuel pump & when you flick the key off & then on that probably fires the pump just long enough to give a start. Assuming the fuel rail pressure is OK then it sounds like AFM or TPS. There is a link to Clarkes Garage on the 944 section which has details of AFM testing & repair. If the rail pressure was way out then I'd expect it to drive badly.... AFM from a Bosch dealer is circa 200-280 depending on model. The dealer will need the actual part no on the AFM itself. Dead AFMs normally give poor low speed driveability. Which you don't seem to have.
Probably worth getting the emissions checked by a friendly MOT test centre. Sure you haven't got a fuel leak elsewhere?

[OK what it sounds like is happening is that you are not getting a prime from the fuel pump & when you flick the key off & then on that probably fires the pump just long enough to give a start. Assuming the fuel rail pressure is OK then it sounds like AFM or TPS. There is a link to Clarkes Garage on the 944 section which has details of AFM testing & repair. If the rail pressure was way out then I'd expect it to drive badly.... AFM from a Bosch dealer is circa 200-280 depending on model. The dealer will need the actual part no on the AFM itself. Dead AFMs normally give poor low speed driveability. Which you don't seem to have.
Probably worth getting the emissions checked by a friendly MOT test centre. Sure you haven't got a fuel leak elsewhere?[/quote]
Thanks again Jim,
The car drives really well in all circumstances when started. I'll check Clarks Garage for AFM testing, and we are checking for fuel leaks but nothing fould.
I'll report back.

Steve

Thanks again Jim,
The car drives really well in all circumstances when started. I'll check Clarks Garage for AFM testing, and we are checking for fuel leaks but nothing fould.
I'll report back.

Steve[/quote]

Check the fuel tank fill pipe is not perished, also the hidden pipe work behind the pup cover under the tank.

WELLLLLLL, the problem seems to have been the temperature sensor that fits into the cylinder block. This apparently was telling the system to pump too much fuel into the engine causing the problems starting and the strong smell of petrol.

It's a bit early to say all the problems are solved but OK so far.

Regards

Steve