My car idles a little rough, is there a way to test or tell if maybe one of the spark plug wires is arcing. I noticed that two of the wires on the driver side were touching one of the air tubes. Would the heat from the tube be enough to damage the spark plug wire?

 

Yeah, that heat will burn the wire. You could take them off to examine for cracks, or at nite start the car and see if you see any small sparks.

 

Place your finger where you think it is sparking from with the motor running. Then you will know for sure.

 

you can usually hear an arc very easy too. it makes this loud "snap...snap....snap" noise.

But yeah, if its arcing from one wire to another it will burn the insulation on the wires.

 

yeah try pulling a wire while the engine is running....youll know lol i did it on a friends car...he thought coil packs were going out in his grand am...well the one i pulled was good and shocked the crap out of me...made my whole body numb for a minute it felt kinda cool tho

 

I used to work at a tune-up shop.
When the first distributerless ignition systems came out we didn't have the adapter to hook up the big Sun scope.
What we did was power-brake eng aggressively, and have someone spray the plug wires with a water spray bottle.
If the wires were bad, eng would start having a fit; missing, crossfiring, etc.
Replace plug wires and spray test would pass every time.

Luckily, the customers were in the office watching Oprah.

 

I don't know how things are done today, but in the old days, (carbs and points, not horse and buggy )we'd just pop the hood at night with the motor running and look for it.

 

I do that trick after every plug wire change!

 

Sorry, but I have to be a spoil-sport here. It's not a very good idea to pull a plug wire when the engine is running. 2 reasons:

1. It's not good for your health. I heard tell of people having heart problems from such practice, especially with aftermarket coils, or DIS systems.

2. It's not good for your electronics. You could potentially fry you module, or various other components when the spark doesn't go where it should, because it had to find an alternate route.

The water spray test is what I have always used. I never really worried about revving the engine, or power-jacking it, because the water will usually find it without.

Good luck, and be safe!

 

There's a reason we power-braked eng when doing the water spray test.
If a plug wire was marginal, It would work OK at idle, but leak upon eng acceleration.

Reason being; air is an insulator, as you open throttle, more air enters combustion chamber.

Now there's more "insulation" within the spark plug gap.

Even though the spark plug gap remains the same, more voltage is now required to jump the gap.

The increase in voltage can trigger the spark to find an easier route to ground, like out the side of a plug wire.

 

I understand WHY you would power-brake them, I've just never had to go that far with it. Most of the time I find it at idle.

Sometimes, you can find them without visibly seeing an arc, water test, or anything other than a test drive. It all depends on how it is missing. I guess a bad dist cap can act like a bad wire will, too, but I like to replace the cap and rotor at the same time as plug wires, since you have all the wires off the cap anyway.