Major plug wire corrosion at coil.

[Cheddar_Dan]

Hey All!
Am chasing a cold start miss/rough idle issue and started pulling plug wires from coil one at a time immediately after last cold start. All seem normal except one. It and/or plug wire end are snow white corroded like a forgotten flashlight battery!! Only the one. Plug wires are 5 years old with 30k miles on them. Question: why the corrosion on one and only one so bad it has eaten half of the plug wire connector??? yes, it's time for (at least) a new plug wire, but is it time to toss the coil or can it be cleaned or is corrosion coming from the coil, maybe?? Seems really odd to have only one sign of that kind of krud.

BIG THANKS!!!!!

 

[Gary Crist]

That is the spark arcing away the metal the was once there. You found a miss!
GM HEIs grew lots of that fluff.

 

[Roadrunner777]

Does it look a little like this?

You could make a trivia question these days to identify this part. It is, of course, the inside of a distributor cap. If this gunk looks like your gunk, it is the byproduct of arcing. I have seen it in distributor cap spark plug wire sockets too... like, 40 years ago. My thinking is, at least at one time, there was a loose connection here and some arcing as a result. Replace the wires and clean up the socket at the coil pack.

So, I was sitting here ready to complete this post and I started thinking about your cold start issue. Could this alone cause your problem? Is this actually an obscure symptom of a bad coil pack? The coil pack fires plugs in pairs, as I guess you know. Could it be that there is an internal issue that is causing the other of the pair to disconnect and dump all the energy through this one, causing the residue?

Coil packs are about $30, which is right around the border of what I will spend on a part without definite proof of fault. I think I might pre-emptively replace the wires and the coil pack. If I wanted to spend time proving it out, I suppose I would work out the pair of this plug and check it with a spark indicator gizmo while it is acting up. Up to you, it's -14 degrees where I am right now, I would just replace the wires and pack and see what happens.

 

[Cheddar_Dan]

Parts order placed!! Thank-you, All!!

RE: "Does it look a little like this?" Yes, pretty much but worse.

 

[Cheddar_Dan]

UPDATE: Odd, "two-minute-when-cold" stutter/miss has disappeared after I replaced coil and (damaged, single) plug wire. ---that also took care of low RPM/under strain cut-out. Check Engine Light came on after a while and (best I can tell) tossed 176, 543 & 111 codes. I have since replaced driver side o2 sensor. Will test drive tomorrow to see if codes disappeared or changed.

Finger's crossed!

BIG THANKS, ALL!!!
.d

 

[Cheddar_Dan]

No Check Engine Light this A:M !!!

 

[Roadrunner777]

Well, good news, another '94 running happy. I think some nice afternoon when you have nothing to do, you might pull the spark plug associated with this problem, particularly if it's an easy one to get to, and look it over. Or not... Sometimes on older stuff the old 'if it ain't broke...' theory is best. Up to you! Glad to hear it's fixed.

 

[Cheddar_Dan]

pull the spark plug associated with this problem, particularly if it's an easy one to get to, and look it over.

What am I looking for specifically, please? Thanks!

 

[Roadrunner777]

Well, I'm just thinking that plug got some abnormal energy from the coil. I'm not thinking of anything specific. It was really just an idle thought, not a concern.

 

[Cheddar_Dan]

Well, I'm just thinking that plug got some abnormal energy from the coil. I'm not thinking of anything specific. It was really just an idle thought, not a concern.

Thank-you! I replaced all the plugs since the photo I posted. Finger's Crossed!!!