Join Date: Aug 2010
Location: Kansas City, KS, USA
Re: HELP Please - no power under load
It is unlikely that the intake valves would be eroded since they run cooler than the exhaust valves, and valve erosion doesn't happen overnight. Also, you probably didn't work near the Hall effect sensors, so chances are good that's not the issue.
The wiring diagram seems to indicate the coil actually consists of two coils, one for cylinders #1 and #4, and one for cylinders #2 and #3. With #1 and #2 acting strange, it is doubtful that the coil could be bad since that would mean both coils developed the same problem. The Hall effect sensors also seem to provide dual signals relayed to the respective coils, and again it doesn't make sense for cylinders #1 and #2 to show a problem but not #3 and #4 due to the layout.
The only other culprit I can think of is the Motronic control unit, but again it provides separate signals to the two coils. Cylinders #1 and #4 would fire together every 360 crankshaft degrees, and #2 and #3 would fire 180 degrees later but also every 360 degrees. It is probably worthwhile to double-check the plug wiring. Correct orientation is engine 1,2,3,4 from the front, and coil 1,2,3,4 clockwise with #1 at the lower left. Is it possible that #1 and #2 were swapped around?
BMW MOA #140995
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