I know you can do it with an ohm meter, but can plug wires go bad and not show signs in the resistance? I'm asking because I have 2 plugs that keep fouling and I'm hunting the problem down. I tested the resistance and got anywhere from 600-850 ohms (Taylor Spiro Pros). Nothing out of the ordinary. The wires are 3 years old and maybe have 12,000 miles on them. I also tested the coil wire, which is a different brand, and got like 4,200 ohms. Is this my problem? It's between the plug wires and the injectors, and I was just needing to know if the wires can be bad and it not show with an ohm meter. TIA.

 

Well you could do it the old fashion way. With the engine at idle pull the number one plug wire off. If the wire and plug were good the engine rpm should drop. If it either were bad the rpm will not change. Repeat for the rest of the wires. Use an insulated tool so you don't get shocked.

 

It won't help if the cylinder is misfiring some of the time.

 

I know this is an old post but I am having the same problem. I have one cylinder where the plug was fouled, so I replaced the plug but I am still getting misfiring on that cylinder. That is the only cylinder its doing it on. I have red Taylor wire and on that wire I am getting 680 ohm resistance, even if that is too high for a Taylor wire, is that why I am having misfirings?

 

What exactly does the fouled plug look like?

 

Swap wires with another cylinder and see if the missfires follow, if it does, then the wire is bad.

Dirty, black.

 

Or.... maybe you have corrosion in the Opti terminal for the wire.

A wire can "go bad" because the insulation has broken down. That will not affect the resistance of the wire. But it will allow the spark to jump from the wire to a nearby metal surface, or between two wires.

 

If you don't know that the resistance reading you are getting is good or not, compare the reading to another wire where the cylinder is having no trouble. Resistance will vary by wire length.