Hi. I picked up my 325ci yesterday. When I first got in it I noticed that the acceleration in the low end was sluggish, picking up in the mid and really shifting in the high (around 4k rpm). I took it to a friend's to check over before a long drive home, seemed fine but when I went to start it would run for 2 seconds then cut out. Turned out it was the MAF sensor, showing a lean code on OBD. Unplugged the MAF and it started no problem. The low end picked up a little but still sluggish. The question is; was the sluggishness to begin with (before maf failure) down to a faulty maf? Also is it worth trying to clean the maf and resetting the fault with OBD before buying a new one? This car has a cold air intake so could it just be dirty? Thanks in advance
Tezza365
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MAF sensor failure
Disconnecting the MAF sensor is NOT a good test of if it is working or not, unless you are looking at other data. Usually you have a large vacuum leak (and lean code) and disconnecting the MAF sensor causes the DME to revert to a default rich fuel/air map, which then masks the vacuum leak.
Use your OBD scanner/software to observe the following at hot idle and report back.
www.e46fanatics.com
Use your OBD scanner/software to observe the following at hot idle and report back.
- trouble codes
- short term fuel trims, banks 1 and 2
- long term fuel trims, banks 1 and 2
- MAF value (in grams/second)
- RPM
- Coolant temperature
OBD Fusion
If you have a smart phone or tablet, get an OBDII app and wireless adapter to see exactly what is going on with the engine fuel management system. A quality OBDII tool supports the following: Diagnostic Trouble Codes (DTCs) in Pxxxx format (such as P0171) Individual emissions readiness...
www.e46fanatics.com
Thanks for the advice. The maf has defo failed as when plugged in the engine cuts out so had to disconnect. Check engine light isn't coming on though. The only fault the obd picked up was a running lean fault. I have had a long drive since so will plug back in and see what codes it throws up.
My $0.02 is that if the MAF is causing the engine to not run, then you will have a MAF code, P01nn, not a lean code. If you have a lean code then you have a hole somewhere that is allowing in air that the MAF does not know about, and since you do not have code that specifically says that the MAF is not working, then it is working and something else is wrong.
One of the the common points of fail is the bellows in the duct that takes air from the MAF to the throttle body. The bellows can get cracks at either the peaks or the valleys.
THIS IS THE WRONG DIAGRAM, BUT YOUR INTEREST IS Item 3 in the diagram that is your car. You could find something else wrong, but this is one of the biggies that you have to check.
One of the the common points of fail is the bellows in the duct that takes air from the MAF to the throttle body. The bellows can get cracks at either the peaks or the valleys.
THIS IS THE WRONG DIAGRAM, BUT YOUR INTEREST IS Item 3 in the diagram that is your car. You could find something else wrong, but this is one of the biggies that you have to check.
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