Originally Posted by NW Cascade Rider
... And both TB's showed evidence of back fire / miss fire. ... Is there a good alternative coil or a coil with the same part number that would be a good replacement?
Common to see black soot in TB's. Characteristic of the engine from the lean burn.
Good explanation on the ignition sl-b-fast
The 1100 coil, unlike the 1150 dual spark, is pretty robust. Pull the coil and check the resistance cold and heated with heat gun. The published resistance is wrong in many manuals. Check the spark wire resistance. Solid core so they usually don't go bad but the insulation weakens and energy can jump to ground. Can see at night. BBY and EME. EME use to carry the Bosh coil packaged with a plug wires for cheap but now only seems to have the wires:
edit: Slardi beat me to it! Wonder why the supply of the new style Bosch has dried up. Maybe the revised Bosh coil was nfg. What is BMW selling? I've been lucky with my old Bosh coils. I f Rick says the "early" ones were weak then he ought to know. Got to be a substitution out there but mounting will be an issue.
I would still resolve the loose tank liner and pull the intake manifolds when you get a chance.