The reason for this is the fact that natural propane gas instalations are made to these engines to save on fuel
and I had propane tank in the trunk of the car. I
removed that installation from my car,
since it took too much of heat from the
heating (engine coolant used to warm up the propane ). After the replacement when I drive on gasoline
the mixture remaines too rich thus the need to go back and make that adjustment first if it was altered by the previous owner.

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Poland 300 miles E of Berlin Germany