Rough Running - Ignition Coil out?

[ZR1CK]

I have a '91 with just under 27k miles and am on my 3rd set of ignition coils. Bought the car in '01 with 10k miles. Replaced the Delco's because one was miss firing at around 18k miles with Accel. Had same problem with them at just over 1k miles. Found out that the are no longer made in USA. Third set is BWD, made in USA, and just recently had one of those fail. Don't know what the problem is, maybe they can't handle the heat. Any thoughts?
Rick J

[A26B]

Did the bad coil actually test bad once it was removed from the coil pak base? With the failures you describe, I would be checking the harness connectors to the base and possibly even the base. Do you recall which coil failed for each of the 3 different events?

Your problem is certainly not the norm.

[ZR1CK]

Hey Jerry, good to hear from you, thanks for responding. It all started one day when the motor seemed to be skipping. After eliminating that it was the plugs, I turned to the plug wires and ignition coils. The way I checked them is by using my timing light to see if the plug wires were carrying any signals. Six of 'em were signaling fine while two were intermittent, and those two were tied to the same coil. I then popped off the plenum, checked all the plug wire connections at the coils, checked all other wiring connections that I could get at for snugness and then swapped two of the coil positions. Put it all back together and ran it, this time two different plug wires were intermittent and tied to the same coil, the same one that was missing prior to the swap. To do another check, I disassembled everything again, removed all 4 coils and took them home (I rent a garage away from home) and installed them one at a time in my '99 Buick which used the same coil application. 3 worked normal and the one that was missing on the "Z" was also missing on the Buick. I decided to replace them with Accel coils because of their reputation over the years. But, at around 1500 miles that same problem occurred. So much for reputation. This time when I took it apart I did check the base plate for continuity and it checked out good. I then decided to check the primaries and secondaries of both the Accel's and the previous Delco's (yeah, I saved 'em). They all read within specs with my ohm meters, both of them, I have 2. The only thing I can figure is that the insulation on the windings is breaking down to a point were they can be read good with the ohm meter but when a high voltage is applied they fail. I figure it's because of the heat on top of the engine. So, this time I decided to replace them with BWD coils as they were made in the USA. I have a "thing" about that. I found that the Accel's are made in either Taiwan or Mexico, can't remember which. Anyway, the BWD's were working great for about 8k miles. Same thing, one coil failing. Coils shouldn't breakdown that soon. My '92 Blazer has over 200k miles with the original coil and it works 4X more than the "Z" coils. I'm gonna need to make some kind of a change. I'll let you know.
Be "Zeeinya"

[Paul Workman]

I've nothing to add to your conclusions or decisions: I'd be doing something similar.

However!! (and you did touch on this too), HIGH VOLTAGE devices can frustrate attempts to "OHM" them out using the standard DVOM/VOM. And, the reason (in case some are wondering) is high voltage can punch through (arc!) insulation that has cracked or deteriorated/weathered), or current pushed by high voltage can take a surface route to ground, especially if the surface is covered with moisture or salt or rust...any number of impromptu conductors. And, frankly the standard VOM is powered with (at most cases) 1.5 or 9 volt battery(s - neither being high enough to cause arching/shorting and thus being detected by the VOM.

To directly test/measure stuff like wire insulation or continuity requires a tester such as a MEGGER (a high voltage "VOM" used for measuring the resistance of insulation or spark gaps).

However, I doubt you'll ever see a MEGGER at your local auto parts store: would be unusual if you did! So, much as I HATE indirect testing, substitution with a known "good" device may be the next best alternative. But, here's the rub: How do we know the replacement is any good? And, HERE is the place where so many times ppl get in trouble: they ASSUME the 'new' device is good, and therefore if the problem persists or returns shortly thereafter, they don't verify the issue is not withe the new part. (See how often in threads like this where someone says: "It can't be (this or that) because it was just changed a short time ago!" The most failure prone time for a new device is immediately (or soon thereafter) it is first put in service!! Never assume a new part is not bad based on time in service...NEVER! Verify operation.

NOTE: And, since so many parts come from over seas, the trend is a lot of (electrical especially) parts just don't last like the OEM parts if they work at all! Just sayin.

[ZR1CK]

Hey Paul, thanks for your response and additional info and explanations for others out there. I am familiar with a megger as I was an industrial electrician. Being that I am retired now I don't have access to one. And one thing I did do when I was working is to check the operations or work-ability of items, new or refurbed, before installing them, even though my colleagues mocked me, to verify they were good to go. One of the things that greatly frustrated me was to install an inoperable "new" or "refurbed" item. Anyway, I did replace the latest "bad" coil with a same BWD coil. Car runs like it's supposed to now. I also relocated the coil pack from the top of the motor to get it away from the heat. I suspect that that's what was causing the problem. So far the car is running very well. If you are going to Carlisle I can show you what I've done.
Zee ya

[XfireZ51]

If you haven?t done it, do the coolant bypass on the TB. Makes a plenum pull soooo much easier and quicker.

[A26B]

Rick,
You have been a thorough as can be, spent a lot of time, but you have confirmed bad coil(s). The fact that it did occur is very unusual. I have a question remaining.... Did the initial coil failures by some coincidence, all occur at the same coil position, i.e. 8/5 location, or 4/7, etc., on the coil base?

[KPW]

Originally Posted by XfireZ51

If you haven?t done it, do the coolant bypass on the TB. Makes a plenum pull soooo much easier and quicker.

Like the bypass line Marc Haibeck sells? Wouldn't I also need to block at the injector housings to get the full "easier and quicker"?

[Paul Workman]

Originally Posted by KPW

Like the bypass line Marc Haibeck sells? Wouldn't I also need to block at the injector housings to get the full "easier and quicker"?

Not meaning to get off topic, and certainly not arguing w/ Marc Haibeck, but I drilled and tapped and plugged the TB coolant ports at the IH. To avoid any air bubbles, I remove the cap from the side of the coolant pipe (drivers side) and fill the system there. I've done this a few times now, and haven't had any issues with air bubbles.

That said, Marc's method came to light AFTER I had done the plugging method. And, to do it over again, I would likely go that route instead of plugging the IH. But, either way REALLY makes pulling the plenum a SNAP!.