PDA

View Full Version : Stumped - V6 Mustang Spark Issues



mikelemoine
11-30-2010, 11:28 AM
Hi all,

I've been trying to solve a problem with my daughter's boyfriend's car with no luck and was hoping someone could give me some ideas. It's an 04 V6 Mustang that started misfiring with around 83K on the odo. It had the original plugs/wires and I popped the hood at night to discover a cool little lightning show going on in the engine bay due to bad wires. Changed the plugs and wires with Autozone's best (mid-grade wires and autolite platinum plugs, gapped at factory spec) and it ran great for about an hour, then started misfiring again. I popped the hood again and found the wires arcing again, just not as bad. I checked to make sure the wires weren't touching anything that would burn or chafe them, they looked perfect but they do sit on the intake manifold, so any leakage has a nearby ground.

I assumed the wires were defective and had him take them back to Autozone. They said that even though they were the midgrade wires, they were the same as the premium ones and they've never had complaints about them. They swapped them out under warranty and we installed them. Again, no arcing until he drove it for a while, then back to the same problem.

I can't imagine that it could be anything else but the wires, but it just doesn't make sense that two sets would do this.

Comments:

The new plug wires looked fresh (box was nice and new, wires soft and pliable, weren't on the shelf for years!).

Haven't checked for codes but no CEL.

Old plugs were clean but worn, gap had increased to .070-.080 (supposed to be .051-.057, gapped new at .054).

On the second set of wires, I used zip ties and some split loom to isolate the wires from any potential rub points or contact points.

I told him when we first opened the hood that his problem was he was missing two cylinders! I told him he needs to trade up to at least the new Stang V6 to regain his manhood.http://www.nhtoc.com/vbforum/images/smilies/rotfl.gif Poor guy, I give him a lot of crap....
http://www.nhtoc.com/vbforum/images/statusicon/user_online.gif http://www.nhtoc.com/vbforum/images/buttons/report.gif (http://www.nhtoc.com/vbforum/report.php?p=553782)

Thanks in advance for any suggestions.

mikelemoine
12-01-2010, 11:25 PM
Bueller,,,, Anyone?? Bueller?

http://instructing.com/wp-content/uploads/2010/08/bueller_stein.jpg

L8 APEX
12-02-2010, 08:22 AM
Maybe the ignition module is a problem and is shooting out insane voltage.

mikelemoine
12-04-2010, 12:46 PM
Maybe the ignition module is a problem and is shooting out insane voltage.

Thanks Terry, I am leaning in that direction too. The old plugs were really worn (double recommended gap size) and the wires had been arcing for a while. I suspect that overworked the coil and may have damaged the primary, which will increase the current on it and the voltage on the secondary. Going to try swapping it to see what happens.

Take care.

mikelemoine
12-13-2010, 12:49 AM
Terry nailed it, the coil pack fixed the problem.

It's mounted on a side angle facing away from the manifold, so with the plug wires disconnected the spark would have to jump a long way. Some cyls had a strong spark jumping around the coil pack back to the manifold, while #3 was too weak to do it unless you held a screwdriver (grounded) up to the end of it. Put a fresh CP in it and it ran great.

Too bad it's still a V6 LOL:vomit:

Thanks Terry!