maf again? p1128 p1130, hesitation, running rich , stall

[pgboxters]

My car has about 89k miles on 2000 S. cleaned maf went away came right back ordered a new maf.

[JFP in PA]

1 hour ago, pgboxters said:

My car has about 89k miles on 2000 S. cleaned maf went away came right back ordered a new maf.

This combination of codes indicates that the engine is running so rich that the DME cannot correct it.  Sources of code can be one or more of the following:

• Incorrect MAF signal
• Fuel pressure too high (often failed fuel pressure regulator)
• Leaking injector
• EVAP canister purge valve stuck open

[crwarren11]

I had a similar problem not too long ago with the same codes. In my case it was a leak in the intake tube between the MAF and the throttle body. I used a smoke tester to locate the leak, repaired, and it has not come back.  In the past I have dealt with these simultaneous codes and they have also been leaks in the intake (rubber boots cracked and/or torn between the plenum, loose connections of the same, cracked hose from the AOS). As others have said there are several root causes which you should not ignore but from a relatively easy first step I would look for sources of unmetered air getting into the intake after the MAF. If it is bad enough to cause a stall then it might be obvious…this usually happens to me when I forget to put something back together after some work that required removal of the intake and/or plenum. 

[pgboxters]

A Follow up,  new maf finally got the right part #, no more codes but still runs alittle ruff mostly start up idle long terms are still neg but less. Don't know what else to check. Everything is new. Aos,plugs,coils.a dealer replaced the bad alternator with a bad rebuilt one? Still noisy sometimes.  

[JFP in PA]

As the car had been running rich base on the old codes, you may need to run it a bit at speed to clean off the plugs.

[pgboxters]

Today I got bad idle on a cold start up practically stalling and like a mini backfire. So I checked all the clamps . Has alot of power but bucks and notchy in gear at times. Has original fuel filter.  So not fixed by replacing maf no codes yet.  

[JFP in PA]

It still looks like it is struggling with an overly rich mixture.

[Makrilli]

Is 6 g/s MAF reading normal for you at idle?

Because that's more than normal.

Have you tried to unplug the MAF and see if the car runs any better?

And the new MAF is a Bosch part right?

Edited October 27, 2023 by Makrilli

[pgboxters]

i got a bremi maf this time seems to work fine porsche seems to be double displacement for maf idle 3.2 x2 = 6. fuel trims around 3 -4 now. there is a little hickup when the idle kicks down during warm-up.