BMW E30 mass air flow sensor and mixture adjustment
How do I clean the carbon track of an E30 mass air flow sensor?
Open the meter's cover and wipe the carbon track with a lint-free cloth and alcohol or isopropanol. Do not use an electrically conductive substance or CRC. Also wipe the tip of the needle carefully, and seal the cover back on so that no moisture gets in.
How is the mixture adjusted with the mass air flow sensor?
Fine adjustment is made with the hex screw on the meter body or by moving the adjusting plate one tooth at a time, because a small change is enough. The effect of the screw shows mainly at idle. The adjustment is best done using an exhaust gas measurement.
How does a faulty mass air flow sensor show up, and when should it be replaced?
The meter is a wear part. Symptoms are uneven idle, jerking and a flat spot in acceleration. An oxidised contact surface and worn tracks may be fixed by cleaning; otherwise the meter is adjusted or replaced. The meter cannot be swapped from one engine type to another, for example an M40 meter does not work on an M10.