Maf sensor

[2bmws]

probably been asked before but here it is.
When i bought my z3 it idled real bad, i put a new icv on it, new intake pipe and ive changed the smaller diameter pipe that comes off the inket pipe as that was split, plus i bought another maf off ebay for it. It idles a bit better but still not great.
Anyway i was having a nose under bonnet messing with air bag plugin, and the car was idling i thought wonder if it will idle better if i disconnected the maf.
So i unplugged it and nothing happened no change in engine note, now how do i test the maf as this is a second hand one or even test the wiring going to it
Cheers

 

[mrscalex]

The most likely conclusion is the replacement MAF is duff. You would be rather more unfortunate if it was the wiring.

 

[NZ00Z3]

What year is your Z3?

Which engine does it have?

Do you have a scanner so that you can do some engine checks and measurements?

 

[2bmws]

I have that cheap b800 scanner

 

[2bmws]

And because theres no change in engine note or a hesitation when i disconnect it, must be a dud

 

[Pingu]

You can test it with a voltmeter...

 

[2bmws]

Thanks

 

[colb]

Maf's either work or work badly or do not work at all, they do not always set fault codes and can be difficult to diagnose, best view them with scanning software that views live data so you can see what it is doing e.g. amount of air passing through it in galls per sec to give you an idea if its working or not. Unplugging a Maf will allow the car to run on defalt settings so if its bad you should notice a difference in running on default settings if the Maf was bad it should run better on default settings. Air leaks in any of the intake and vaccum hoses are the most common cause of poor idle and performance, air leaks will be picked up in the exhaust as its seeing more air than what was reported passing through the Maf so it thinks its running lean. To correct what it is seeing it will richen the fuel at the injectors and will continue doing so until it reaches around 20% more fuel being added, it gives up at that point and sets the engine management light on the dash. Scanning it with an OBD2 scanner will reveal a code for high fuel trims, usually caused by air leaks or maybe a bad Maf. Never buy cheap pattern Maf's they seldom work or for long, stick to OEM Bosch or Seimens, you take a chance buying used parts even if they are OEM. If your Maf is bad and you replace it with a good working one you will notice the difference immediately, when mine went duff,I replaced it with OEM and it transformed the car.

 

[2bmws]

Fitted maf, running much better now

 

[mrscalex]

You can test it with a voltmeter...

Very good that thanks @Pingu . Now bookmarked.

 

[Chamber66]

Maf's either work or work badly or do not work at all, they do not always set fault codes and can be difficult to diagnose, best view them with scanning software that views live data so you can see what it is doing e.g. amount of air passing through it in galls per sec to give you an idea if its working or not. Unplugging a Maf will allow the car to run on defalt settings so if its bad you should notice a difference in running on default settings if the Maf was bad it should run better on default settings. Air leaks in any of the intake and vaccum hoses are the most common cause of poor idle and performance, air leaks will be picked up in the exhaust as its seeing more air than what was reported passing through the Maf so it thinks its running lean. To correct what it is seeing it will richen the fuel at the injectors and will continue doing so until it reaches around 20% more fuel being added, it gives up at that point and sets the engine management light on the dash. Scanning it with an OBD2 scanner will reveal a code for high fuel trims, usually caused by air leaks or maybe a bad Maf. Never buy cheap pattern Maf's they seldom work or for long, stick to OEM Bosch or Seimens, you take a chance buying used parts even if they are OEM. If your Maf is bad and you replace it with a good working one you will notice the difference immediately, when mine went duff,I replaced it with OEM and it transformed the car.

Hi Colin
My car has been sitting for sometime and is now running on 4 cylinders instead of 6
I have swapped the coils about so I know they are fine. Could it be the MAF sensor?
Car smells rich

 

[2bmws]

Has the problem followed the coils when you have swapped them about, have you put new spark plugs or swapped them about to see if the problem follows the plugs. If you unplug the map sensor does it stop misfiring as it will run on a sort of safe map. How old is the fuel as the new stuff does go off you can put a fuel stabiliser in, is the wires to the coils ok, any faults on the dash as could be a bad cam or crank sensor

 

[Chamber66]

Just add its been scanned and no faults showing
Swapped coils over but still 1 and 4 not running.
That's as far as I have gotten so far. I will check the injectors tomorrow