Would a bad sparkplug wire cause:

by all means spark can "jump" or travel through a bad or broken wire. eliminate yor problems by replacing both the plugs and wires. use only O.E. PARTS. (ORIGINAL EQUIPMENT) then have your car hooked to a competent scanner to locate further problems. it will save you $$$$$$ that you will undoubtably spend by simply replacing parts.

Yes 'and' yes for number 1, No for number 2.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

snipped-for-privacy@yahoo.com wrote:

it seems economy is a primary concern.even if just on principle.what i do is remove end off wire and cut back to good "wire"1/2 inch at a time.then put end back on.then test wire for spark by putting back on coil and sticking a spare sparkplug in boot and grounding.(lay on engine)do not hold plug while engine is turned over.or just replace that wire.if problem persists.consider complete tune-up.

I might add that on modern engines a certain amount of resistance is expected in the spark plug wires. So many Kohms / foot. If you are within a factor of 2 of the factory specs, you might be able to trim the wire back. But if you get into the 5 or 10 factor range of error, you can screw up your ignition module and ruin your engine.

The ignition module in a modern engine is _designed_ to expect a certain resistance in the plug wires. The plug wires are in fact part of the design parameters for the ignition pack.

It is a good idea when buying replacement wires to check them with an ohm meter, to be sure you are _close_ to factory specs. Or you can fry some stuff in your engine, the main thing being the ignition module. And then you replace it, and fry it AGAIN. And this shit keeps going on forever, because you =have= to be within tolerance of the design parameters for the 30,000 volt and up circuit.

It is best to stick with OEM wires from a dealership when replacing your plug wires. And route them _exactly_ as the originals are routed, or you can have *crosstalk* between them, which will further screw things up.

Pay the extra bucks and get OEM wires from the car dealership. And it isn't only a matter of the resistance, the insulation characteristics of the wires are just as important.

Penny wise, dollar foolish, when it comes to replacing or *shortening* plug wires.

Lg

since the voltage going thru the plug wire is an result of indirect voltage generated in the coil windings how would the ignition module be affected?where is the feedback encountered?even though a system is designed for a certain plug wire resistrance,does this does imply a catastrophic failure due to being out of spec.the only thing i can imagine is the coil either internally or externally shorting its high voltage to nearest ground which could be the module in the case of a highly resistant plug wire(misfire).is that what you meant.

I have had 'missing' when wet issues when stuck way back in the deep bush and have cut off a couple wire ends and put them back on. I carry a multimeter though so I knew when I had good wire.

The last time I did this, I drove an extra 75 miles return from the trail head when I went out for gas to get new OEM wires before going back to the campsite which was 25 miles from the nearest house.

In my mind, once a wire has gone rotten, it is time to change the wire and the distributor cap that it plugs into. A good shot of dielectric grease helps keep them from rotting.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

I think it is a question of how much current is being supplied by the ignition module, not just a voltage issue. If you're running plug wires that have a much lower resistance than OEM, then you're demanding more current from the Ignition Module during each plug firing. Over time ( how much? )...this can't be a good thing for the Ignition Module. It could/would lead to overheating of the IM, overloading of the circuit providing the spark voltage.

If you're saying that the coil is self-limiting in the amount of current it =can= deliver, because of its design, that is right, so the means of damage is unknown until/unless I can get a schematic for the IM in question. All I can say, is you will find this information on the WWW regarding plug wire resistance and the necessity for it to be correct for the circuit in question.

I suppose you can do a Test and report back to this n/g with your results. Run Stranded Copper Wire instead of spark plug wire, from your IM/coil pack to your plugs. If you make it to town and back, be sure to open the hood to see where the smoke is coming from.

Lg

The ignition module _does not_ supply current. It switches the primary current on and off, nothing more.

Secondary resistance has absolutely nothing to do with primary current. There _are_ methods of identifying secondary resistance problems by analyzing primary current, but that would be getting a little ahead of the game in this case. The particular vehicle in question _does_ employ circuitry to limit primary current independent of secondary resistance and/or voltage.

Happens once the secondary resistance causes secondary voltage to exceed the dielectric strength of the weakest component of the secondary which usually happens to be the shellac coating the windings of the coil secondary, but it's strictly a function of voltage, not current.

He's asking about trimming back a few inches of the plug wire and re-crimping the terminal at the end where the wire fried. No big changes there once one considers that this is well within the differences in plug wire length normally found on such a vehicle.

Copper core plug wires cause EM type interference and are likely to radiate electrical noise that other sensitive circuits are unable to cope with, the ignition coils themselves probably wouldn't care one bit.

That is my experience too, Mike. You might jury rig a wire and get back to civilization, but it is false economy to 'doctor' spark plug wires. The carbon conductor wires can be fragile enough without cutting on them.