Coil Problem

[XfireZ51]

Originally Posted by Locobob

Ugh, and now I'm having more annoying issues. The throttle appears to be hanging up sometimes. Won't rev down on coast down occasionally and sometimes the idle is a little high, both cured by a blip of the throttle. I pulled the airhorn and checked the throttle blades, cleaned up the IAC and reset the TPS to .54 (it was slightly low at .52). Don't see any issues when manually manipulating the throttle, it appears to snap shut just fine every time. Hmmmm

Bob,

Did you disassemble the throttle blades?

[Locobob]

No I did not disassemble the throttle body or remove it from the plenum. That issue seems to be better so I'm focusing on the original problem of the ignition system. Looks like I'll have to pull the plenum again. Need to take another look at the plug wire on number 5, it ohm'd okay on its own but I didn't completely remove and inspect it, perhaps it rubbed on something and is grounding? Also going to check the wires between the coils and the DIS module.

[LGAFF]

Any chance something is arcing off the starter, thinking of the fuse problem I keep having on the 91 build

[Locobob]

Fuses look good, no codes set.

[Locobob]

I also checked the primary side of the 8-5 coil I removed and it OHM'd within spec so it appears the coil is not the root problem.

[Locobob]

I just talked to MSD's tech support and they are favoring a problem with plug wire #5, specifically a bad connection where the wire snaps on the coil tower causing arcing and corroding the tower. The wires are Magnacore and probably 10-12 years old. Looking at the ignition schematic from the DIS each coil has its own hot wire and two coils share a ground. This would seem to limit the possibility of a problem with the DIS module, phew, I hope.

[XfireZ51]

If you haven't already, how about just starting the motor and then twisting the #5 plug wire to see if u can induce a miss. Obviously protect yourself from any
shock.
Also wait till it's dark out and then start the motor. See if any arcing is visible either under the plenum or from wires.

[Locobob]

Originally Posted by XfireZ51

If you haven't already, how about just starting the motor and then twisting the #5 plug wire to see if u can induce a miss. Obviously protect yourself from any
shock.
Also wait till it's dark out and then start the motor. See if any arcing is visible either under the plenum or from wires.

Yeah I think I'll try killing the lights and looking for an arc. I've heard it's a bad idea to pull plug wires on a running engine though.

[XfireZ51]

Originally Posted by Locobob

Yeah I think I'll try killing the lights and looking for an arc. I've heard it's a bad idea to pull plug wires on a running engine though.

Not suggesting u pull the plug wire, but try twisting it and see if it affects anything.

[GOLDCYLON]

Originally Posted by Locobob

I just talked to MSD's tech support and they are favoring a problem with plug wire #5, specifically a bad connection where the wire snaps on the coil tower causing arcing and corroding the tower. The wires are Magnacore and probably 10-12 years old. Looking at the ignition schematic from the DIS each coil has its own hot wire and two coils share a ground. This would seem to limit the possibility of a problem with the DIS module, phew, I hope.

Swap the coils around and see if the problem persists. to rule out bad coil / Wire