slslave

I have a 2001 Grand Marquis taxi. About a month ago the number 4 coil went out. I had it replaced. 4 days ago my car shuts off while I am driving it and wont start. I take it in and they find the number four coil out again and the first relay. They replace it and take it out and about 3 minutes on the road and it goes out again. So 3 times now the number 4 coil has been replaced and then last night it shuts off and wont start. I wiggle the relay box and the car starts right up. They are thinking a short in the computer or a wire not grounding but we can't find one anywhere. Anyone have any ideas or the same problem?

Aussiblue

Use a noid light (usually used to check fuel injectors but it will fit the wires to the coils - inexpensive from any autoparts place) to see if the wire to each coil gives the same brightness when you turn the engine over; if not for the number four it should tell you something. Also check the integrity of the wiring harness to the number 4 coil to ensure there is no chance the wires have been reversed. Also pull the sparkplug and check that it has the correct gap and no damaged insulators or signs of shorting (might be easier just to fit one new spark plug), also check with a multimeter that the earth wire to coil is earthing.

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Regards Blue