NB & NCII V8 Fairlanes
Join Date: Feb 2001
Location: Bibra Lake Western Australia
Re: This has everyone stumped
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.