Mass Airflow test?

[fridgemiester]

Is there any way of testing the MAF meter on a 1998 m3?

[mmm-five]

If you disconnect it and the car runs the same, then the MAF isn't working!

[fridgemiester]

Ok.

I have a really rough idle at the moment so if I disconnect the MAF it should run of if it is US?

[mmm-five]

If you disconnect the MAF and it gets better/worse then it's likely to be the MAF, but it could also be TPS, coil, plugs, O2/lambda sensor.

[evobob]

or more than than likely a broken connection on vanos exhaust solenoids..
mine had a broken/ bad solder joint which caused it to run lumpy on tick over.

[_Neal_]

I'd bet solenoid as well

[TheEnd]

If there is a change when you unplug a MAF, all that will tell you is that the air/fuel mix was wrong.
Maybe due to the MAF, an airleak, lambda sensors etc... It's not a great way for finding a problem, and to top it all, it'll now put a MAF error code into your ECU if you ever get round to getting the codes read.

[TEKNOPUG]

Find someone with sound running engine and swap the MAF over.

[fridgemiester]

OK and now for the next exciting installment!

Went to start the car this morning had a flat Battery. jump started fine filled up at local garage drove 60+miles no rough idle no misfire!!!!

Any ideas? dodgy fuel at last fill up? jump start spiked ECU and wiped faults???

[fridgemiester]

Update

Fault is back!

[TheEnd]

Fault code reads next.
Other possibilities are the TPS, or a little vacuum cap on a T piece under the engine creating an airleak.

[fridgemiester]

I have checked all hoss and infamous t piece all look ok. you mention TPS?

[TheEnd]

It's a common problem on both the 3.0 and 3.2 engines where they get old and worn and cause issues without any major clues.
You could test it with a multimeter, looking for any jumpy areas.

[fridgemiester]

Cheers mate !
still not sure how to test if you can supply an idiots guide it would be greatly appreciated. if the sensor was playing up and it was disconnected would this improve the idle or make it worse? also any idea of replacement cost? just checked fleabay and range from £10-£50

[TheEnd]

I don't know if you could tell much by unplugging it, but to test it, you'd need to either probe 2 pins, swing the throttle and watch the resistance figures, or...

probe the pins with it still connected, and look for about 0.5-4.5v smoothly increasing as it opens.

[fridgemiester]

Great info.

Just checked youtube lots of stuff on there.

Many thanks