Both the pump and filter are preventive maintenance items. I was talking about fuel pump.
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Gotcha. I thought the fuel filter was never replaced.
As far as the maf, when it's disconnected and the car runs better, the maf actually has a soft fail. The ECU defaults to a base map with it unplugged ( car will run rich )
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So found a really good BMW specialist here and what we found after rechecking is that there are no vacuum leaks with a high degree of certainty.
We did find that the fuel correction value in the ECU was stuck at 12%. He said this should change based on O2 signals and MAF readings and RPM. Wasn’t moving even with MAF disconnected. He actually said MAF was reading correctly.
I had the shark injector tune on the car so I reverted back to stock and saw the same thing. The value is an internal tune value so not sure why it’s stuck.
I’m planning on taking it to have the ECU reflashed to factory and then have the dinan stage 3 put on it as they should be able to do both at the same price and see what we have.
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I don’t remember, but from what he was telling me that should have been moving around with throttle input and when he was spraying some brake cleaner into the pcv system when we were looking for vacuum leaks. And it never changed.
The only concern I have is an issue in the ecu caused by the shark injector tuner since basically the whole manual is a warning about damaging your ECU.
My plan is to take it to a dealership that can do a software update and install fresh on the car, and potentially put a Dinan stage 3 tune since it has throttle body, exhaust, and intake and check the trim value again.
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Your mechanic should have noted the short/long term fuel trims at idle and at 2500. If the numbers dropped down when the engine rpm was increased, it would point to a vacuum leak. If the numbers did not change, the you are either looking at pre-cat o2 sensors, maf sensor or a fuel related issue ( fuel filter or fuel pump )
Spraying brake cleaner is not the proper way to diagnose vacuum leaks on these cars. You need to use a smoke machine which would easily pin-point any small or big leaks.
However if the fuel trims were at 12% which are really high, I would look into points of entry after the maf sensor like the disa o-ring or the throttle body boots. You can remove the disa and see if the o-ring is seated properly or inspect the throttle body boots for any tears. But you also mentioned that the car ran better with the maf disconnected so cleaning it with some maf cleaner could yield some improvements.
So the DISA has been replaced and we are replacing all 4 of the O2 sensors. I’m also going to go ahead and order the boots so I have those done too.
We were going to recheck the O2 sensor function and the fuel trim again. I have the fuel pump and filter on the list for next months car budget.
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Pulllling this one back up. So I get the car back from paint today, and going to get back to work. Just a quick update on whats been done and whats getting done.
Work Completed (updates in Bold):
- New Dinan Air Filter
- New MAF
- New Upper Intake Boot
- DISA Valve Replaced (New)
- New Plugs
- New Coil Packs
- New Upstream and Downstream O2 Sensors
- Reflash of ECU to stock at BMW
- Fuel Trims Noted prior to Reflash, will be getting them rechecked
- New Main Fuel Pump and Fuel Filter
Even after all this, car still has some weird low end hesitation and issues up top occasionally. Read a few places that Cam Position Sensors may cause issues with low end problems so this is what I have next:
- Intake and Exhaust Cam Position Sensors
- Lower Intake Boot (ordered)
- CCV System (although didn't seem to have any blockages when it was in the shop)
To continue the discussion on fuel trims... I don't know what the numbers mean in context but below is the print out I got from BMW. I plan on taking the car back in and having them pull the trims again since I've put some miles on the car since this measurement was taken and the ECU was reflashed:
- Adaptation, mixture, bank1, additive: 0.72 mg/Hub
- Adaptation, Mixture, Bank 2, additive: 0.44 mg/Hub
- Multiplicative bank 1, mixture adaptation: -8.00%
- Multiplicative bank 2, mixture adaptation: -8.00%
Nice werk
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