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Dagumpf Dagumpf is offline
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Join Date: Dec 2018
Car: BMW E93 N54 2009
Default Trims variance and misfire - 10-11-2020, 04:20 AM

Running 26psi (4.5k rpm) to 21psi (6k rpm) with CP WMI. JB4 + custom BEF.

Since installing the WMI and new turbos to achieve this, I have been having a cylinder 1 misfire when hitting 6k rpm (very occasionally misfire on cylinder 2 or 3 as well). At around 4k rpm WOT, Trim2 becomes 5-8% higher than Trim1 all the way until 6k rpm. However, with WMI off and lower boost, trims remain the same and no misfire.

All plugs are new, 2-steps colder and gapped to 0.022". All injectors were replace not so long ago, although I have replaced (and coded) cylinder 1 injector and coil (Eldor) again with no change.


I can't visually see any intake manifold leaks/marks, not sure if I would.

Would like some advice on how to fix this. Some of my thoughts:
1) There is a boost leak on the intake manifold somewhere - but would think I would see some marks from such; and also the dropping boot doesn't lead to a closing closer on the trims.
2) I am having some blow-by on cylinder 1, but not seeing anything bad in terms of the oil or in the catch-can.
3) The Water-Meth isn't mixing well in the intake manifold, but I would expect to see a trim differential though-out the rev range, and would also expect more fueling to bank 1, not less.
4) Valve issue; intake or exhaust valve leaking? Could bad valve stems seals or guides cause this?

Any other suggestions before I take the head off?
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Last edited by Dagumpf; 10-11-2020 at 04:32 AM..
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