AMF sensor: replace or not replace

poloxi · Dec 27, 2011

Hello I need some opinions possibly regarding the AMF sensor on 2001 e46 330xi.

The engine light lights up when the car is started in cold weather. It stays lit for a few days then it turns itself off. The idle is not really rough but could be smoother.

OBD Code states that the right and left banks are running too lean. No vacuum leaks have been found, the oxygen sensors are ok, and CCV is ok.

I cleaned the AMF sensor with the appropriate cleaner but it did not help.

For the sake of science I am willing to do an experiment: either do nothing and see what happens (anyone knows what terminal damage could come from that?), or replace the AMF sensor possibly with a factory refurbished for 190$ (local store parts). Also amazon has some cheap “new” AMF sensor for 65$. Has anyone tried that?

Thank you all

Spikes007 · Dec 27, 2011

I guess you're talking about the MAF sensor? If you are sure you looked up everything and you want to buy a new sensor, stick with OEM. There is a lot of stories after using an other brand for sensors on a bimmer.

jvr826 · Dec 27, 2011

Are you certain you inspected the intake track carefully? Cracking in the intake boot is a common issue as these cars age. But, I would expect other codes and symptoms to surface.

What about the fuel delivery system? Has the fuel filter been properly maintained? Good fuel rail pressure?

Obvious things... is the air filter clean, properly seated, and the air box sealed up as it should be? Are you running a non-stock air filter, maybe an oiled version like a K&N drop-in or aftermarket CAI?

smolck · Dec 27, 2011

JVR826 is on the right track. Id get a smoke test done. If you dont want to do that, pull all the pieces from airbox to throttle body and give them a good once over, including in the creases of the accordion like parts. Chances are you'll find a hole(s).

poloxi · Dec 28, 2011

Good morning and thank you for your replies,

Spikes007 is correct, we are talking about the MAF.
I have a new OEM air filter, the smoke test turned out negative, but when the dealer installed a good mass air meter the "adaptations reading" (whatever that means

went back to normal.
So we are back to to the MAF sensor: Napa has an OEM refurbish for 230$ and they will give me 75$ back for my old one, amazon has one for 65$, and autohauzAZ has a VDO OEM for 200.
I am thinking of buying the VDO.
It will take a few days before it gets here, meanwhile I still have to drive the car. does Anyone know what damage I may have done by driving the car (for a while now) as is with "adaptations readings" at 7 and 6 instead of 3 and 5?

Thank you all

smolck · Dec 28, 2011

poloxi said:
does Anyone know what damage I may have done by driving the car (for a while now) as is with "adaptations readings" at 7 and 6 instead of 3 and 5?

None. Car may run like crap, but it won't cause permanent damage. In fact, you may just pull the MAF connector off, forcing the car into a "default" setting and get better performance till the new MAF arrives. If it doesn't make it better, just plug it back in.

EDIT: IF you have an automatic trans you can't disconnect the MAF, it'll throw a trans code.

dslboomer · Dec 28, 2011

You are okay because your engine is running lean. If it is rich, it may harm catalytic convertors.

AMF sensor: replace or not replace

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