![]() On cold start up engine rpm was most often shooting up to between 2.5K and 3K rpm, then quickly going down. ![]() Of course the SES light was on because of above codes Fault Code thrown: 2D06 value HFM to high (OBD version: P1424 Mass or Volume Air Flow Too High) Fault Code thrown: 2A2F Mixture too rich (OBD version: P0175 System too rich bank 2 ) Fault Code thrown: 2A2E Mixture too rich (OBD version: P0172 System too rich bank 1 ) For instance 328 N52's are using different part number MAF even though the MAF from outside looks very much same physically and could be prone to same problem. Yours may be using different part number MAF. To start the long story, I have a first year (2006) US N52 (325XI) with a certain MAF sensor part number: 13627520519. Summary for TLDR people: MAF sensor connector was not making solid good connection due to too may connect disconnect cycles over 10 year service the life of the car and also due to what I believe too thin connector pins on the MAF sensor side for the connector pins used. I am only sharing my experience with no claim that what I describe here is safe or correct way of working on the car. If you decide to use what I describe here, use your own judgement, safety, consult BMW shop manuals or trained mechanics. What I am writing here is my own experience and I can't give any guarantees what I describe and explain is correct information or the right and safe way to work or do to a car. Some disclaimers: I am not a trained mechanic. After long trial and error and some testing and research I am confident I found the root cause and wanted to share since I saw other old posts with same problems with no conclusions to solutions from other people. If RPM increases when a spot is sprayed, that is where the leak is.This is a post of sharing my experience with a difficult to diagnose stubborn "system too rich" and occasional "Mass or Volume Air flow too high" codes being thrown with SES light and idle and some drivelability problems. If you have a spray-can of ether or "Starting Fluid," on a COLD ENGINE, immediately after startup, spray some on the hoses under the rear of the intake manifold, and listen for any increased RPM. Most frequently-reported cause I have seen recently on this Forum is cracks/ breaks in the hoses related to the PCV and Oil Separator, allowing "un-metered" air (air that did NOT pass through the MAF) to be sucked into the engine. The voltage supply to the MAF could be an issue, or any wiring or connector fault between the MAF and the DME (loose/ corroded/ damaged pins/sockets in at the connector, damaged wiring, etc.) could also cause it. Basically, that signal is "out-of-range," completely lacking, too high or low voltage, etc., or the signal does NOT suggest measurement of the amount of air that should pass the MAF at a certain engine RPM.Ī faulty sensor COULD be the cause of such codes BUT, so could a leak in the ducts between the MAF and the intake take manifold, or even manifold gasket leaks. The two FC you list: 2D06 & 2D0F, both have some relation to the SIGNAL from the MAF as received by the DME. Fault Codes should NOT be viewed as identifying WHAT COMPONENT to Remove & Replace.
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