stewartld

Hi,

I've got a 992 2003 C2 cab. It's been stood for about 2 months whilst I was travelling. I came back to the expected flat battery, it wouldn't hold a charge so I've changed it. I took it out for the first time today and it's running very roughly, stalls as soon as I take my foot off, no ABS, no PSM...Any thoughts or suggestions?

Thanks

DBJoe996

E-gas? Recalibrate. Turn key on, do not start engine, wait one minute, then turn car off. Stumble could just be the ECU relearning it's curves and the car needs to be driven for several trips. No ABS or PSM...don't know. Any Check Engine Codes?

C4CRNA

MAF sensor needs cleaning.

Zookie

NEED NEW MAF don't bother cleaning it, been there done that

stewartld

Definitely seems like the MAF sensor...I tried cleaning it which didn't work but disconnected it and the car runs fine. The ABS and PSM lights are still on but I guess a new sensor will sort that?

Is the flat battery just a coincidence or could it be connected?

Macster

Flat battery just a coincidence.

Reads like MAF is bad.

The behavior of the engine coupled with the fact you disconnected the MAF and the behavior improved certainly points a finger at the MAF.

Also, that the ABS and PSM warning lights are on is another accusing finger pointed at the MAF.

My understanding is both ABS and PSM need (among other things) a derived value -- engine load -- that is supplied by the DME and the DME derives this from -- in part -- from what it gets from the MAF.

If the MAF is acting up the engine load value is goofy and well, the ABS and PSM warning lights can be on.

stewartld

Thanks guys...new MAF sensor on order...

Macster

Do not throw the old MAF away. While I don't think this is the case in well, this case, I mis-diagnosed a MAF when it proved to be a leaking oil filler tube cap.

After replacing the MAF and the symptoms -- CEL and forgotten error codes -- came back the leaking cap was ID'd and replaced. Skip now ahead a few years and nearly 100K miles and the engine started acting up again. I do not recall the symptoms now but this time I again diagnosed the MAF as the source of the problem.

Remembering I had saved the old and apparently good MAF I dug it out and swapped it with the suspected bad one and the symptoms were gone.

Might add more recently I found the replacement oil filler tube cap leaking and replaced it yet again. Figure around 100K to 150K miles to an oil filler tube cap...

Ahsai

Have you tried the e-gas recalibration Joe suggested yet?

Note sometimes it's normal for the ABS and PSM lights to go on after a battery change and they will go out once you put some miles on the car.

stewartld

I tried the recalibration but it had no effect...

Ahsai

Did you turn the key to the last position before cranking and leave it there for one minute withoit touching the gas pedal? You should hear some high pitch noise and clicking from the throttle body when it's calibrating itself.

If that still has no effect, I agree the next suspect is the MAF. You can use an OBDII scanner to check the MAF reading. Should be about 4g/s at idle when engine is warm.

stewartld

Yes, tried the recalibration but it didn't solve the problem...