A4 2.0 TDI MAF problems
Discussion
I,ve got a A4 2.0 TDI 2005 BLB with the engine light that keeps coming on with p0101 maf performance problem. I,ve changed the maf twice within a few weeks, every time the same. Its done over 100k. I,ve checked for boost leak but cant find anything obvious. Checked intercooler appears ok. It appears to drive fine and boost ok although kicks out quite abit of black smoke. Anybody have any ideas or had anything similar?
If it says MAF, its never the MAF.
Its either a boost leak or an EGR fault. Sadly both present with exactly the same symptoms, MAF fault and black smoke.
SO either look harder to find the boost leak, to be fare if you have one, you should be able to hear it, or take the egr valve off and look at it.
When the A4/A6 elctronic EGR valves fail when the actual flap moves indipendantly to the shaft its on. SO although the motor is working and the shaft moves to the closed position (so no fault code) the flap is still a bit open and you get to much EGR, this means the MAF reads lower air flow that it should for the specified RPM (so you get a MAF code.)
The look like this.
Best way to test is to remove for inspection but with the wires still attached and final control them with VAS 5051 or VAGCOM, you can see the flap moving back and forth and see if it is sticking on not moving correctly with the shaft.
Its either a boost leak or an EGR fault. Sadly both present with exactly the same symptoms, MAF fault and black smoke.
SO either look harder to find the boost leak, to be fare if you have one, you should be able to hear it, or take the egr valve off and look at it.
When the A4/A6 elctronic EGR valves fail when the actual flap moves indipendantly to the shaft its on. SO although the motor is working and the shaft moves to the closed position (so no fault code) the flap is still a bit open and you get to much EGR, this means the MAF reads lower air flow that it should for the specified RPM (so you get a MAF code.)
The look like this.
Best way to test is to remove for inspection but with the wires still attached and final control them with VAS 5051 or VAGCOM, you can see the flap moving back and forth and see if it is sticking on not moving correctly with the shaft.
Edited by Tame Technician on Tuesday 25th May 23:11
Ok will check. It had a new egr actuator a year ago and egr cooler. Took it to friends audi specialist garage to test maf on 51 and found under load aprox 3000rpm it was showing 1350mb of air flow when it should of been 1500mb so only slight problem, harder to find. garage didnt really have much answers checked intake manifold flap bolted egr unit appeared ok.
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