E60I

That is very interesting! It sounds to me like you can not even "feel" the difference when the MAF Sensor is connected or not. In a way, that's kind of great.

I have a 2006 530i (N52 Engine), and currently it does not run if the MAF Sensor is connected. The engine would crank for a second and that's all it does. When I disconnect the MAF sensor, the engine would run, but VERY ROUGH. I already ordered a new sensor and can't wait to receive it!

For the sake of curiosity, can someone with a 2006 530i (N52, automatic transmission) do me a favor? Would you mind start your engine with and without the MAF Sensor connected and describe the results for me?

Much appreciated if you can do that favor. Your findings will certainly help some of use understand how the N52 engine behaves in the controlled conditions.

pcy

On my car, as expected, car runs roughly with the MAF disconnected and smooths out as soon as I connect the MAF.

Essentially, when you disconnect the MAF, car computer doesn't know how much air is going in to the engine (in order to figure out how much fuel to mix). So, the car computer goes in to default/pre-set air/fuel mix ratio. Since that default/pre-set mix is not accurate for the amount of air going in, engine will run rough.

nbbmw

HI,
its an old thread but thought i'd chime in. i have a 2007 530xi with 211k and a MAF that's never been changed. so I started the engine and pulled the plug from the MAF sensor.
The engine still ran but just slightly rough. plugging it back calmed it a little. I wonder if its time to change my MAF sensor? anyone with thoughts?

seanjordan20

If you don't have a code there's no need the MAF is doing it's job.

tstiglich

For a number of reasons, the computer or ECU will try to maintain a fixed (may vary under certain conditions) air to fuel ratio. One way to do this is with a MAF (mass air flow) sensor. If the mass of air coming in is known, then the mass of fuel to be delivered can be determined. Some cars do not use a MAF sensor, but rather a MAP (manifold absolute pressure) sensor. This is called the speed density method of determining the mass of air entering the engine. To determine the mass of air, one needs to know the volumetric efficiency of the cylinders, the intake air temperature, etc. I assume that when the MAF is not present, the ECU will operate in some sort of limp home mode. In doing so, it will look at various parameters to estimate the MAF. It will be off. Too rich, you take out your catalytic converter. Too lean, you burn out your pistons. In summary, it is not an optional part.

seanjordan20

Ok with all that (thanks for the explanation by the way) what is your answer? Should it be changed or not?

The point I was making was these cars are very smart. If the MAF was on it's way out (not sending the correct signals) or dead a code would be thrown hence me saying if you are not getting a code there's no need to replace it.

tstiglich

As others have chimed in, unless you are getting a MAF error code, I would not replace it. What error codes are you getting?

tstiglich

I suppose that I am lost here. Is your car experiencing problems?

tstiglich

As for whether or not the MAF is operating correctly. I don't know. I do know that there are a number of sensors, O2 for example. They output a voltage proportional to the input. Suppose that the output signal is 0 to 12 volts. What the actual sensor will do is output a voltage of 0.5 to 11.5 volts, as an example. Anything less than 0.5 or greater than 11.5 is a fault or a short. But, in the end, as long as the signal remains within these extremes (and varies, ie not stuck on a specific output), I suppose that there is no way to determine that they are operating correctly without additional information from other sensors.