"BMW Z3 Mass Air Flow (MAF) Sensor - Replacement Warning"

Ron Stultz

2 March 2013

Thanks: Valle Altobelli

Summary: BMW's MAF is expensive and you could be tempted to use a cheap, after market, version. Well be warned it may or may not work for you.

Background:

From Valle Altobelli.

1997 BMW Z3

Failed California emissions testing.

Check engine light (CEL) "on".

As part of do-it-yourself (DIY) effort to solve CEL, after market MAF bought and installed.

MAF - After Market May or May Not Work Correctly.

In Valle Altobellis case, had the wrong type O2 sensors installed causing CEL and emissions fail (click here for details).

But after market MAF installed also over-reporting the airflow by 20% compared to the original (seen via on-board-diagnostics (OBD) laptop software), causing the short term fuel trims to saturate trying to compensate and after a few minutes the fuel system went open loop.

Know there is significant cost difference between BMW dealer MAF and some aftermarket MAF's but be warned that if you buy an after market, it may or may not work for you.

CEL problems can be a bear to solve and you do not add to your headache by installing a component you assume is good (i.e. new) when it may or may not be "good".

If you have concern that your MAF is not operating correctly, you could remove and try to clean the very thin wires inside using MAF cleaner that is sold at auto parts stores. Just be careful as MAF wires are very, very, thin.