Service Engine Soon light will not go away

[fernando306]

Car runs fine, but acceleration is lumpy and uneven. Sometimes it goes like hell, sometimes it hesitates and bucks, very unpredictable.

Fuel trims are on the negative side and sometimes check engine light shows up because it is running too rich. Injectors are fine, fuel pressure is fine.

I thought MAF would be a long shot, until I saw it yesterday that it is a damn crappy 20 dollar chinese MAF.

[fernando306]

Would this one be fine? Or it needs to be THE genuine MAF?

https://www.fcpeuro.com/products/bmw-ma ... 83#reviews

[Smartbear]

Guys,

My MAF is chinese. Just saw it yesterday.
What brand MAF can I safely use? The BMW is $400 bucks, VDO is $276. Any other recommendations?

How does the car run with the maf disconnected?
Rob

The ECU has a stock map for fuelling, if you have rough running and disconnect a suspect MAFF and it runs fine, that suggests that input signals from the knackered MAFF are the likely cause ........... or so I have read on here previously

I know this, that’s why i asked the op how it ran with the suspect maf disconnected
Rob

[Ewazix]

How does the car run with the maf disconnected?
Rob

The ECU has a stock map for fuelling, if you have rough running and disconnect a suspect MAFF and it runs fine, that suggests that input signals from the knackered MAFF are the likely cause ........... or so I have read on here previously

I know this, that’s why i asked the op how it ran with the suspect maf disconnected
Rob

Ahhh "how (well) does it run disconnected", rather than "how does it run when disconnected" (as in how is it able to)

[fernando306]

My friends, I ordered a new MAF from FCP Euro. It's a VDO MAF. We'll see!
I totally forgot to try running it without the MAF.

[Smartbear]

The ECU has a stock map for fuelling, if you have rough running and disconnect a suspect MAFF and it runs fine, that suggests that input signals from the knackered MAFF are the likely cause ........... or so I have read on here previously

I know this, that’s why i asked the op how it ran with the suspect maf disconnected
Rob

Ahhh "how (well) does it run disconnected", rather than "how does it run when disconnected" (as in how is it able to)

That’s the one
Rob

[magicman]

this could be stretch but maybe a leaking injector, might not be seating properly. Do you have any trouble starting? or if you have a fuel gauge, hook it up and see if the rail holds pressure

[fernando306]

I haven't yet read the MAF, but I've replaced it and drove off, immediately noticed better response at low RPM and that the throttle response seems more even. It might just have done the trick! I'll report back later with the values and fuel trims.