The sentence "Low available voltage, high resistance paths to ground" has nothing to do with "I already thought about voltage supply and grounding points. I have cleaned connections and changed bad ground wires."

I am refering to secondary ignition. High resistance paths to ground carry spark voltages to ground instead of to the cylinder. This is intermittant as the resistance would be such that as long as the voltage stays below a level the spark goes where it is supposed to. As the voltage requirement goes up the path becomes the lowest voltage path, taking out that cylinder or all cylinders if the path is from the rotor or coil wire.

A low available voltage means that (for example) a coil only puts out 15kv (should be 30kv or more available). At idle cold the engine might only need 10kv to fire the rich mixture of warm-up, but when warm as the required voltage hits 15kv the fire goes out.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician