M73N: MAF plug & Play? Maybe not...

[TheAngryBear]

TLDR: anyone else find that you have to do a “reset” (KP2 for 30 seconds till TB clicks) for a MAF replacement?

Vehicle: 2001 750iL
Miles: 131K
Symptoms:

• light rough idle
• Bank 2 P0100 MAF voltage value exceeded
• loss of cruise control when code active
• All the misfire with cutoff codes possible for Bank 2

Action taken: replaced Bank 2 MAF with Bosch OEM part

After replacing the one MAF for Bank 2, I still had an idle issue. It would surge to 1000 and drop to 450. Any load and it was fine, smooth as butter.
Coming to a stop and idling though and idle hunt with an occasional stall for good measure.
Thinking “bad MAF?” And hoping not as they are expensive and old/new situations were both bad, I wanted to explore what else could be done.
Back in the E39 days, a simple throttle body reset (KP2 for 30 seconds till the TB cycled, key out, then start) actually resolved a bunch of issues. Not knowing if this was applicable, and thinking MAFs were plug and play, I tried it.
Sure enough, smooth idle and no more issues.
Maybe with the dual MAF, the DMEs need to synch the TB and base MAF numbers for equal torque?
Anybody else experience this?



2001 750iL DD74441
Stock

RIP: 2003 540iA Sport GS56111
H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1

[acspecialists]

Not a 750 guy but I think I remember reading you have to do both MAF's? Make sure you do a smoke test for vacuum leaks before you drop another $400 on a MAF>

[MKIVJZA80]

looks to be pointing to your throttles

[TheAngryBear]

Not a 750 guy but I think I remember reading you have to do both MAF's? Make sure you do a smoke test for vacuum leaks before you drop another $400 on a MAF>

Good idea. Not outside of range (no SES/code on that) but will check trims and if 5% or more do that.

looks to be pointing to your throttles

Found the full reset procedure from Mayorchuck and DUMD and seemed to work even better.

And for public knowledge
KP2 for 3-5 seconds
Accelerator to kick down 3-5 seconds
Release accelerator for 3-5 seconds
Accelerator to kick down for 3-5 seconds
Release for 3-5 seconds
Key out for at least 10 seconds



2001 750iL DD74441
Stock

RIP: 2003 540iA Sport GS56111
H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1

[CPHES]

Yes, I remember having to do this

[S61Dan]

Just fyi, M44 MAFs are the same as m73 mafs. I have 2 junkyard 318 m44 mafs currently on my m73. I had a horrible idle problem and surging at speed. Had a MAF code stored for both units weirdly enough. Changed both with the used m44 mafs and performed a throttle sync for giggles. Woke the car right up and fixed all issues. Been fine for last 400 or so miles.