experimental MAF reset switch: which circuit to interrupt? more complications

[workingonit]

Originally Posted by BimmerBreaker

...Their goal is to provide the correct reading when they have more airflow. Your goal is to trick the DME into reading an incorrect MAF signal

I appreciate your concern, and I understand why those others were modifying their MAF signals, but still, if by tricking the DME into reading an incorrect, but not TOO far from correct, MAF signal, then perhaps I can make up for the assumed (cheap $20) MAF sensor's built-in inaccuracy. I had no hope for the original Siemens MAF after that last trip, so it was sacrificed for science.

I might not use my device, at all, if my preliminary tests are unsatisfactory. I still have the emissions and safety inspection to pass, later this month, so it'll most likely be November before I'm ready to try.

[workingonit]

https://xoutpost.com/bmw-sav-forums/...-no-start.html

And, before anyone says that I screwed up my X with this project, I never touched the MAF, DME, or anything. No tests were ever done.

[workingonit]

It's been two months since I literally shelved my plan to use the "MAF tuner" project box, made to trick my MAF into adjusting the lean fuel trims to lower single digits. I've tried everything else, in 3 years to find the base problem, and have had little-or-no success doing so. By shelving the plan, I mean that I installed the box on a shelf in my home office/"lab", after I decided to not try it yet, and to use it as a variable power supply, instead.

And it's been one month since the new battery was installed, but the X hassn't been driven since then, until today, when we drove to the ranch, retracing the journey last taken in the X, 3.5 months ago, when I gave up on my old Siemens-VDO MAF https://xoutpost.com/1240914-post21.html, which brings me to today's latest MAF weirdness.

Before the drive, I did a once-over underhood, and found the MAF plug loose (unchecked since testing the removable pigtail/jumper, no doubt), so I reset it, and all seemed OK, except that the engine didn't care whether it was plugged-in or not. By the time I got to the gas station a few miles away, the zeroed LTFT's had already climbed to 6.25, each, and varied from there to 9.0 and back, the rest of the trip down. Another thing, the fuel tank cap doesn't seem to be sealing well, probably original, and I'm replacing it this week...could that be a partial vacuum leak/or what keeps my fuel rail pressure just under 50psi? possibly why I get lean codes?


Ok, resuming the story, coming home, my aftermarket fan speed control wasn't working, so when we stopped at a CVS on the way, I opened the hood again, to check the thermostatic switch wiring (wiggled it, and the fan came on...need to re-tighten), and while there, I reset the MAF again (hoping for better numbers). But, instead, while the LTFT's initially stayed at zero for 15 miles, the STFT's were bouncing up to 12-14!, which I hadn't seen before, ever. Eventually, the LTFT's chimed in, and settled going from 6.25-9.0, again, with much better STFT's.

So, now, I'm looking at buying a mid-range compromise MAF, priced between a $$$ Siemens-VDO and the $ ($20 USD) MostPlus cheapo MAF(s) I've been relying on for a couple of years. I might get a BREMI (made in Germany, always a good thing, and I have BREMI injectors already working fine) from FCP, because if it doesn't fix the fuel trims, then I won't feel the same buyer's remorse that I might feel, if I were to spend the extra bucks on a Siemens MAF.

Or, I might have to try my project box, after all.

One more item: monitoring O2 sensors, the downstream ones are getting lazy, slow to respond, though after awhile function as expected. I'll be using my Foxwell to see if they're working ok ( Torque Pro via Bluetooth is sometimes laggy).

I forgot to mention that my M54 still starts on first crank (thanks to the new battery), never misfires, idles smoothly, accelerates like a scalded dog (if I want to ...and who comes up with such analogies?), and the exhaust is smoke and smell-free.