imdrew12

Hypothetical question: Let’s say my MAF is dead or dying, and I get a cel to warn me about it. I am lazy so I unhook the battery to reset the cel. How long does it take for the ecu to perform another test to see the MAF is bad and throw another cel? Is there a set time or mileage that the ecu waits to perform another “systems check” or would it be instantaneous? How or when does the ecu know when to issue a cel for a minor issue? Just curious.

Thanks
Drew

Mother

When using my durametric tester it just takes a 20-30 sec to throw another CEL after resetting the CELL, but if the problem part is marginal it may take it alittle longer. I have not seen a marginal MAF it either works or does not.

imdrew12

How do you like the Durametric software? I looked at their website and it looks quite in depth. Which package did you go with?

Doug Donsbach

The original MAF on my car was marginal. It began tripping P1123 codes in certain driving patterns (e.g., interstate cruise followed by a stop on an exit ramp) and then started adding P1125 to this code, and then began generating more frequent instances of both those codes in a wider variety of driving patterns. Replacing the MAF solved the problem.

To the OP's question: the DME is constantly evaluating everything it sees and will generate a code if something is out of spec.

Loren

"how often does it check for problems?"
Constantly - depending on the conditions it sets a pending code or sets a code and turns on the CEL.
Not all fault codes turn on a CEL.

imdrew12

What are the consequences of having a bad MAF?

Benjamin Choi

Why don't you just share with the forum what your problem is instead of speaking in hypotheticals, going about it in a rather circuitous manner? This may help you find a quicker resolution to the problem you're having with the car.

imdrew12

I am not having issues. I am thinking about buying a K&N filter(not the CAI) and want to be prepared encase it breaks the MAF due to over oiling. I have read so much contradicting info on this filter and the only ECU experience I have is on my Subaru. So to gain some knowledge on the Porsche ECU and to avoid posting another "CAI Thread" I posted this thread. Thanks for your concern.

Benjamin Choi

Knowing that even the K&N intake doesn't do much for power and there's much discussion around the pains of oiling it (over/under), why in the hell would you go for the aftermarket filter when there's the good OEM filter available?

imdrew12

If you're not going to address the questions I posted, why are you responding to this thread?

Benjamin Choi

Because I can and the question I'm asking of you certainly is related to the original question. Having a bad day?

imdrew12

Sorry for the digression, back to the original question. What are the consequences/symptoms of having a bad MAF? What exactly does the MAF do? I mean I know it measures the amount of air entering the engine and the ecu uses that info to change the fuel mixture. What else does the car rely on the MAF for?

Thanks

Drew

Benjamin Choi

Don't forget who had your back even after you internet stalked me, don't know where all this sensitivity is coming from, but do what you do

https://rennlist.com/forums/showthre...=407966&page=4

Doug Donsbach

Air mass and intake charge temperature are the only things the MAF measures. When either of those things are not properly measured, the engine will not run correctly. You may notice hard starting, surging under partial or full throttle, poor performance, rough or erratic idle, stalling, or other symptoms, depending on the failure mode.

imdrew12

....depending on failure mode? I am not sure I follow. The MAF can have more than one failure point? Thanks for the reply by the way.