MAF RPM RISE

T

thenorwegian

Member
Disconnected maf today and something strange happened.

When i use the brake pedal the rpms rise UP to around 11-1200.

My theory is that there is somekind of vacuumleak, and when i use the brakes/brakebooster which is connected to the vacuum system it causes false air leaking in to the engine.

So it runs lean and rpm rises..?

Anyone heard about this?
 
When you disconnect the Maf the car will run on default settings, why did you disconnect it, have you got any problems with it plugged in? It is possible application of the brakes is affecting the vaccum system as the servo will be using the vaccum. Have you scanned the car for any fault codes and do you have the EML lit up on the dash to indicate a problem?
 
The reason I unplugged maf was to check if it was working proberly.

The car runs OK, no light in dash but it sometimes have a little uneven idle, not much tho.

Also a little high fuel consumption and I also feel like it should run a little faster compared to other BMW I had.

Have not scanned the car yet, should do that obviously.
 
It is normal for the revs to rise when you press the brake with the MAF disconnected. It’s one of the ways you tell if the MAF is dead if it does it with it connected.

You don’t say which is engine you have but if it’s N52, your uneven idle might be sorted out with a valvetronic reset.... https://z4-forum.com/forum/viewtopic.php?f=3&t=113662

The Vanos solenoids are always worth a clean too, and if it’s M54 engine defo a check for split hose on the intake near the MAF...

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So thats normal, thats really good.
Its a 2.5 m54 engine.
Intake hoses are all good, icv is cleaned out and vanos seals are new.

Gonna try cleaning Vanos solenoids
 
You ideally need a code reader to be sure, but if it helps, after I refurbished the vanos on my 2.5i M54 I had an uneven idle.
It turned out to be the solenoid valves sticking. It was a fairly easy job to remove the solenoids, pull the valves out, give them a very light rub with fine wet'n'dry paper, coat with oil and put back in.
For reference, the reader I have told me the camshaft was sticking, but I cannot remember the codes.
 
I managed to dig out my old thread regarding the vanos and sticking valves.
https://z4-forum.com/forum/viewtopic.php?f=3&t=125345&start=15
 
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