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Old 01-22-2013, 09:35 PM   #20
OEM ///Member
Join Date: Nov 2009
Location: Fairfax, VA USA
Posts: 23,025
My Ride: 330CiC, M5, X5, E93
The issue is if the MAF is under reporting the airflow, then the the fuel injector timing is low, which then causes the O2 sensors to read constantly lean, then the DME is constantly trying to enrich the mixture to counter the O2 sensor readings.

The problem is the DME can only enrich the mixture by X amount, there are hard limits and this is why you are getting the current codes. The DME cannot bring the fuel mixture into a proper balance within the limits of the DME.

Long term fuel trims really need to be under 3%, anything 2% an lower, I generally take no action.

Short term fuel trims may be a bit higher, but I generally do not pay much attention to short term trims except at idle as they can dance around quite a bit.

Just make sure the MAF readings are in Grams per Second. If they are really at the numbers you have indicated, you have issues. Let me know what the ambient temps were when you captured the data.

If you suspect anything strange with the O2 sensors, suggest you replace the pre Cats with Bosch and replace both at the same time. Unless they are wideband O2 sensors, you should be able to get them for about $50 each on Amazon.

I will try to recheck my 330 tomorrow with Torque Pro as well, I used my Launch CReader VI tonight as it is far simpler to use than Torque, or at least it is plug and play, I can graph on the tool and the back light does not time out! At 18F outside, I did not want to play around too much!

I would bet your MAF was some Chinese knock off from Ebay?? It could be a really bad OE MAF? Suggest you check for part numbers, vendor name and logos.

I have seen some similar issues that you are running into now with import/counterfeit MAF's. I have no idea where they are coming from, what they look like or how many are out there. Hold onto what you pull off and I may want to get my hands on it to look it over closely.
Solve your misfires, lean codes, rough idle -

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Hidden OBC Menu - Check Voltage, Temp, Fuel Level -

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Lower hose temp switch O-ring - BMW #13621743299
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