intermittent Misfire

[Johnboy]

I took the car out today and it started misfiring badly once I got on it. Took the car back home(2mi.) and found number 5 plug wire had come off coil pack and the spark jumping from the cover plate onto the cruise control cable. Anyway put wire back on with some di-electric grease, also did other plug wires at the same time. What is happening now is under boost (16PSI)it is misfiring or so it appears or maybe timing being retarded. It will happen on/off under boost.Checked coil tower resistances and all were the same around 12.9K Ohms. Laptop did show a little KR of 1.4 or so under boost. I figured I would ask to see if anybody has had this happened or has any ideas before I dig deeper on it.

Thanx

 

[copo]

My '87 GN had a slight miss while crusing above 30 mph and more noticable on the highway. Eventually it started to spit a bit a WOT. Then a week later when I put my foot into it one morning, it went bang and I had lost alot of power. It wasn't firing on 2 cyl. I replaced the coil pack and module and alls ok now.

 

[XLR8]

One of the posts on my coil pack cracked and was arcing and it fried the module.

 

[ESP Products]

Your resistance test does not tell you what is happening under load. Commonly the break-up occurs at or about 14-15 psi with aggressive throttle. If you roll into boost smoother and achieve high boost before the break-up then I would feel safe to say it's your coilpack. It's failing under the heavier load conditions and will only get worse.

Hope this helps,
John @ ESP
ESP High Output Coilpacks

 

[pvt num 11]

Sounds like my problem... They ohm'ed okay, but like it was said, that doesn't tell much, only if they're really toasty or not. I'll have to hit Derek up for his spare, and swap some stuff around.