How finicky are AC Delco parts when it comes to replacing ignition coils?
Should it be an AC Delco coil that replaces the old coil pack? The reason I
ask is because yesterday, I was about 1/4 way into a 120 km trip when the
engine light comes on and the engine starts misfiring, eventually causing
the engine light to flash. I knew why the light had come on because the
same thing happened to me about two months after I bought this car. At that
time, I replaced the coil packs with used AC Delco units from one of my
brother-in-laws junked cars. They worked ok right up until yesterday.
Seeing as how it was Sunday and the only auto parts store that I knew was
open for sure was Canadian Tire, I picked up three new Nieoff brand coils
and installed them when I got home. Took the car out for a quick spin and
it was working great, the engine light was still lit, but not flashing.

This morning, I head off to work and notice the engine light has gone out.
About 1/4 way into the trip, I notice the engine start to stumble again and
the engine light comes back on. It starts flashing again. I couldn't turn
around because of the highway conditions and decided to continue on to work.
Aside from the odd misfire (which BTW didn't seem as bad as with the old
coils) and the engine light flashing and distracting me, the car was working
ok, but obviously not correctly.

Now, when I called the local GM dealership, the service manager told me that
in some cases, they have seen aftermarket coils cause the same symptoms, but
not in all cases. So this is why I wanted to ask the group and see what
others say. If the majority of the group says yes they've also had problems
with aftermarket coils, I will likely return the Nieoff coils to Can. Tire
and have to spend the extra $40 per coil on AC Delco coils.

Any opinions are greatly appreciated,
Sharky

"Sharky" <cl_8ball (AT) hotmail (DOT) com> wrote

you likely have another problem. Coils in general are very reliable and
having so many fail on one car is not even logical.

It is possible that the mis-firing has caused partial blockage of the
catalytic converter because of the excess burning of the unburned fuel in
the exhaust. My advice would be to have the car thoroughly checked by the
dealer or other very competent service agency. You should not have to pay
for anything that does not provide long term solution of the problem.

Good luck. Don Young

Don, I'm pretty sure this problem is related to a grounding issue with one
of the coil packs and not the coil itself. It just happens to act up every
time I remove one of the bolts and it doesn't get torqued exactly the same
way that it was.

Last night, I took the car over to my fathers garage and brought the old AC
Delco coils with me. I know for a fact that the very first time I changed
the coils that they were bad, because the plastic was cracked and allowing
moisture into two of the coil packs. The third did not have any cracks, but
I changed it out anyway because the car has such high mileage (nearly
300,000kms). At that point, I took it to a local garage that scanned the
computer and read that 4 out of 6 cylinders were randomly misfiring. When
it started misfiring again the other day, I wasn't absolutely sure that it
was the coils that were "bad" or "worn out", but the symptoms were nearly
identical to the first time it happened when it was scanned with an OBD-II
scanner.

Thinking I may find a fouled spark plug, I pulled all three of the spark
plugs on the front of the engine. The center plug was obviously misfiring
because I could smell the unburned fuel on the electrode. The other two
plugs were fine, so I traced that single spark plug wire back to the coil
and decided to switch it out with one of the used AC Delco coils. While I
was bolting the AC Delco coil back on, I noticed that the front bolt was not
tightening very well. I pulled it back out and discovered that the threaded
hole was stripped on the mounting plate. The back bolt was ok, so I
tightened it with a nut driver as tight as I could, and then managed to
tighten the front bolt fairly tight by hand.

Now, from what I can tell, the coil uses both bolts to ground itself to the
distributor plate and I think what is happening is the coil is loosening
over time because of that stripped hole and it is losing ground, causing the
coil to misfire. Again, when I started the car and put it in gear to load
test it, the engine ran fine with no hesitation. The engine light was still
on, but not flashing. So today, I think I will go back over and find a nut
to fit the bolt and if it's at all possible, try to fasten the nut on the
underside of the distributor plate I don't know if there is enough metal
left to tap the hole, but I may try that first.

Thanks for the suggestions,
Sharky