Good morning wise ones
I am having a battle with an X3 diesel and I am losing my way a little.
This vehicle will more often than not have little or no throttle response, coupled with white 'cold combustion' style smoke, then all of a sudden it will clear and rev freely almost as if there is a blockage somewhere that is moving about.
It has been to various other places and has some nice shiny new parts - EGR valve ( vac operated) vacuum pump, airmass and egr pneumatic actuator.
It has been having EGR fault codes aparently but when it first came in it had

3FF0 Air- mass sensor Deviation excessive
4B10 Smooth running control Correction quantity too high
4501 Exhaust gas recirculation control Control deviation negative
but now it is only giving the air mass fault.
Actual values at idle show air mass nominal 270 with actual at 500 and the numbers do not alter much if idle or revving.

Scope test shows no change on the digital waveform whether the air mass is in still air or connected.



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I have had manifold off and swirl flaps are ok, I have also disconnected the exhaust in case it was a dpf issue but I keep coming back to the fact that air mass is doing nothing. I have load tested all wiring from AMM to ECU and so I think I may be at an ECU fault.

There is quite a bit of play in the turbo and in an ideal world that ought to be replaced, but I dont want to dive down that road until I can understand what is going on with AMM.

Any thoughts/ testing direction would be greatly appreciated

I believe these also suffer from restricted inlet ports in the cylinder head giving MAF fault codes.

Aidan