Mass Airflow Sensor

B

BlueZ4

Member
My service engine light has gone off 3 times in the last 2 months. All 3 times has been the mass airflow sensor. It idles rough and lags at acceleration.

It seems to me that the problem isn't with the sensor, but something else causing the problem.

The dealer recommended getting my injectors flushed as part of regular maintenance, but they're wanting to charge me almost $200 bucks and I don't want to throw the money away if it's not going to help.

Anyone have this recurring problem?
 
Had a similar issue. Does it reset if you restart the car a few times?

Mine is going back in next weekend for a rescan of the codes. The garage reckon it is a throttle sensor or the throttle motor. The issue throws a mass air flow code, but it also provides a note saying do not change the MAF if the throttle sensor code is present too.

Mine is very irregular. It only happens on restart and not while driving.
 
Not usually. It's weird that you mention that cause it went off a few days later and hasn't been back on all week. The dealer is so far away from me that I would prefer not to drive out there, but if I don't, it's going to come back so I might as well.
 
Happened to me on the gf's previous auto 330i. Sometimes it'd go off on the highway and the car would drop into limp mode (transmission wouldn't go past 2nd gear).

Changed the MAF multiple times. Changed the throttle position sensor too. Turned out to be a break in the wiring loom from the MAF. Sometimes the connection would break causing the Check Engine light, and sometimes it would reconnect. Presumably from driving over bumpy roads / potholes.

Brought it to an awesome independent mechanic here that was BMW Factory trained. He did what the other mechanics did not do. He dismantled the parts to get to the MAF while the engine was running... one by one until the code was thrown. While dismantling the code was thrown... he fiddled around, and the check engine light disappeared and the engine ran normally again. He was able to 'switch' it on and off on demand. So he isolated which wire was the issue. Soldiered in a new one, heat shrink wrapped it, and was good as new.
 
ZED_NOT_ZEE said:
Happened to me on the gf's previous auto 330i. Sometimes it'd go off on the highway and the car would drop into limp mode (transmission wouldn't go past 2nd gear).

Changed the MAF multiple times. Changed the throttle position sensor too. Turned out to be a break in the wiring loom from the MAF. Sometimes the connection would break causing the Check Engine light, and sometimes it would reconnect. Presumably from driving over bumpy roads / potholes.

Brought it to an awesome independent mechanic here that was BMW Factory trained. He did what the other mechanics did not do. He dismantled the parts to get to the MAF while the engine was running... one by one until the code was thrown. While dismantling the code was thrown... he fiddled around, and the check engine light disappeared and the engine ran normally again. He was able to 'switch' it on and off on demand. So he isolated which wire was the issue. Soldiered in a new one, heat shrink wrapped it, and was good as new.
Click to expand...

Funny, we seem to have the same approach here....the computer tells the mechanic what to do instead of them doing things the old-fashioned way and getting their little mitts grubby! :thumbsup:
 
Hi can someone help on this one.

I had an igntion coil replaced to Cylinder 1 about a week ago and all was fine. The we drove to edinburgh and on the way back the Engine light came on. The car was running fine, no loss of power smooth as a wistle, however to be careful I pulled in to the service station called the recovery people who came and cleared the fault code. Any way carried on with the journey and about 2 hrs later Engine light came back and the car was still running fine - no issues. Called the recovery guy who checked both 02 sensors and said they are fine, CAT Converter is fine and cleared the warning light code which was P0420. He did have doubts on the Mass Air Flow Sensor, bearing in mind the car was running smooth with no loss of power, hesitation or missfiring, but in anycase ordered a Mass Air Flow sensor one from Euorparts and replaced it which made no difference.

We then tried both sensors and the car was running fine, we then disconnected the Mass Air Flow sensor completly from the electrical connection block and it made no difference the car was still running fine. Can anyone advise why this is, I'm no expert but would have thought disconnecting MAF would have made the engine revs drop and would have lossed power??????

what could have made the warning light come on in the first place when the car was running fine. The car is a BMW Z4 2,0 on 2005 - 55 plate. Was a modification done on this model?

Look forward to some advice, thanks

Rikesh
 
regarding your removing of the maf sensor - the ecu may move to using the map sensor on your intake mani to compensate for it. if there is sensors on your mani that is..dont know much about the 2.0.
 
My experience of MAFs on other vehicles is that its usually a pretty definitive diagnosis of a faulty MAF if its disconnection doesn't affect lumpy running.

Its extremely unusual to have both a MAP and a MAF though since they do exactly the same thing in different ways....the MAP measures manifold pressure to help the ECU assess air volume and thus fuel requirement, while a MAF measures airflow temperature (or electrical resistance in a hot wire/foil to be precise) to provide the ECU with the same info.
 
Had probs the same as you turned out to be after I looked hard a split in the rubber boot below mass airflow sensor,replaced reset lights and all seem's well. Car never lost power revs rose and sort of stayed there,just the emisson light on the dash. they do seem to have lots of female gremlins that just go away.rubber boot cost me £29.00 5 min job, hope it works for you. :thumbsup:
 
Thanks Guys, I will look at the rubber hoses below the MAF and look for any splits or damage. Can someone advise if the car is safe to drive given there is no warning light on and she drives like normal.
 
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