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'Floaty' Tach and intermittent stalling 700 1990

posted by  Old 740 on  Thu Jan 13 15:37 CST 2005
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The tach is driven from the ignition primary pulse. I think the tach is probably okay and the ignition system is faulty, especially if the car is not running right.

If your tach is jumping around (not the same as your actual engine speed) it means that there is a problem in the ignition primary circuit. Common faults are wiring connections and grounds, power stage, and the hall switch or flywheel pickup depending on which one your car has.

I had an intermittent misfire at high speeds on the highway with my '86 740 and the problem turned out the be the power stage. Replaced it and she runs like new.






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