Running isssue 2.5

dave_monster · Mar 20, 2014

Help,
The last two times I have driven my car it has developed an annoying fault. It seems to be running out of fuel whilst driving along it is a tip tronic and there are no faults logged apart from the MAF sensor. could this be the problem? when it cuts out it restarts again fine but as soon as you attempt to move it stall again. the fault is more apparent once the car is warm...
Many thanks for any suggestions ...

Motorhead · Mar 20, 2014

Quite probably Dave.

Try disconnecting the MAF sensor to see if this cures the problem (the engine should run with a default setting).

Since a MAF fault is logged, you could try cleaning the sensor but it's probably best to replace the component.

Jeff

Glyn · Mar 21, 2014

Agree with Motorhead, sounds like a MAF fault.
unplug the electrical connection from the MAF (leave the MAF in place though) and the car will default to its "limited operation strategy" - this will ignore the output values of the MAF and the system will approximate the air/fuel ratios - In effect the car will now run perfectly fine.
The exhaust gases wouldn't pass an MOT but to the driver the car will feel "cured"

The common issues a driver notices when the MAF fails (which is so common for some reason on the Boxster) Lumpy tickover and slow reaction to throttle input - feels like a misfire, Popping and backfiring when throttling up, hesitation through the mid to high range of revs - the car holds back then power feels restored.
Not all the symptoms happen together and the MAF can fail without warning, switch off and everything is normal - restart and the MAF isn't working properly.

Disconnection (electrically) of the MAF will certainly confirm that the MAF has died - and an easy job to change - just two screws hold it in, check the part number on the old MAF to get the right replacement as their are two MAF part numbers available for the 2.5

dave_monster · Mar 22, 2014

Thanks,
I had removed the MAF and cleaned it.
The odd thing is the car runs perfectly fine for sometimes over an hour then will give the symptoms of fuel starvation, ie it will actually die whilst driving although on occasion will bump back into life, and this progressively gets worse. I have left the car for 2 days now untouched after it ran so badly, and drove it today it all was fine again ???
could it be the fuel pump or a relay problem perhaps?
plugged it in today and no fault codes logged what so ever.

Motorhead · Mar 22, 2014

Dave,

If you're not using Durametric or PIWIS diagnostics, you may not be seeing all the error codes.

Yours is probably a high mileage car, so the MAF may well need replacing rather than just cleaning. Of course, the problem may well be on the fuel delivery side since you're describing fuel starvation-type symptoms; difficult to check-out without specialised equipment.

Always tricky to trace intermittent faults such as yours.

Jeff

dave_monster · Mar 22, 2014

The mileage is only 78,322 so not excessive. Is there anyone in Norfolk with the relevant diagnostic equipment?

Motorhead · Mar 23, 2014

Dave,

Just had a look in Porsche Post and the only Porsche Indy listed is STR Porsche & Mercedes Specialists in Mountergate ( http://porsche-servicing-norfolk.co.uk/ ). There's also Autowerke in Norwich ( http://www.autowerkenorwich.co.uk/ ).

They may be able to advise you.

Good luck.

Jeff

graemewf · Mar 25, 2014

My 2002 3.2S needed this today. It was running a little rough exactly as you described and has just had the Mass Air flow sensor replaced. Seems to be a common problem in a lot of cars. This isn't the first one of these we have replaced - changed these type of things in a couple of other models of cars in the past. The local garage near the house changed it for us after hooking up to the computer and downloading the fault code. They got one sent out from Aberdeen and we are back on the road now. [

]

Graeme,
Ellon,
Aberdeenshire.

Glyn · Mar 26, 2014

Don't understand why you ask for advice then disregard that advice and start considering other components (Fuel pump and relay).
Of course an intermittent fault with the fuel pump or its relay could account for the issues but - to check this out is a cost option.
Better to go with the no cost options first unless you enjoy spending money.
You don't say if you have run the car with the maf unplugged - only that you cleaned it, Maf faults can be intermittent but - It will never repair itself, but, running with Maf disconnected (if it is a Maf fault) will see the car return to normal operation, and if that does fix it you then know for sure the Maf needs replacing.

dave_monster · Apr 1, 2014

Ok, I have now replaced the MAF sensor, for a genuine one, and replaced the fuel and air filters and changed the oil and filter (not that it is that relevant). The car will drive normally for sometimes over an hour then without notice it begins to hesitate on acceleration which quickly develops to what can only be described as fuel starvation. It cuts out even when driving along, it is not speed dependent or affected by revs...

I am at a loss to be honest. In response to Glyn I was not disregarding advice, I was metaphorically scratching my head and thinking out loud.

I do appreciate any and all help thank you..

Glyn · Apr 2, 2014

Time to have the codes read, clearly something is happening intermittently, this could be an ignition fault or an engine management issue such as the oxygen sensors - or indeed an intermittent fault with the fuel pump pressures.

However, you could give Russ a call at Revolution Porsche, he is a site sponsor on Boxa.net and is always ready to help, Revolution has fantastic reviews and all their staff are Porsche technicians - and all really nice guys. Im sure Russ will offer help and advice - tell him Glyn told you to ring