Canging ignition coil as a preventive maintenance?

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PandaBear

PandaBear

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Say you have 2 cars that always fail on the same item within 30k (gasket, O2 sensors, radiators, exhaust manifold, AC, etc) and one of them had a bad coil not so long ago (210k miles). You end up buying an OEM because you don't know if you have time to mess around and buy one on the Internet.

Now let's say your other car already has 180k miles with this coil and it is having a bit more miss fire than you remember from the past, and even with a platinum plug it still doesn't run as smooth as before. Do you go ahead and change the coil as a preventive maintenance, and keep the old one as a spare?
 
I would swap coils, and see if the miss smooths out. Personally I wont change parts till they fail, only maintenance parts, unless the part in question shows physical damage.

I just replaced my brake pads 10k miles ahead of schedule, only because I dint want to do it in the middle of a hot summer.
 
Change it. Assuming it's an easy operation.

Always nice to have a spare, and you have a brand-new one laying around.

I'm a sucker for using new parts, on the assumption on car parts that newer equals better.
 
I'd say try a new coil. You probably won't be out but around $50 if you're wrong. $50 is cheap insurance compared to being stranded on the road, in the dark, in the middle of nowhere, when it's cold, and raining, and . . . . .
 
Originally Posted By: pcoxe
I'd say try a new coil. You probably won't be out but around $50 if you're wrong. $50 is cheap insurance compared to being stranded on the road, in the dark, in the middle of nowhere, when it's cold, and raining, and . . . . .


when your mother is driving this car and she doesn't know much more than steering wheel, gas and brake pedal.
 
I replaced spark plugs (with double platinum), wires, cap and rotor on 305 chevy back 130k miles ago. I wish I had also replaced the ignition coil, because it was misfiring at times for the last 40k miles and the coil was the culprit. Seems like the secondary ignition parts shold be replaced at the same time for optimal service life and fuel economy.
 
I was going to say "no" when I saw the title to this thread but changed my mind to "yes". You can get breakdown in the insulation within the coil that shorts half of it out, leaving the other half with more stress. Worse, it can come and go, driving you crazy because your diagnostic tools are never with you when it's acting up.
 
How long do they usually last? Do they degrade over time and is it possible to diagnose its remaining life?

I'd read somewhere that you should check its resistant at 20C or something like that.
 
I tried to remove the coil in my Cherokee to test it and gave up (just tested it on the car). It's unusually painful to remove considering how easily most of the rest of the Jeep comes apart.
 
The coil on my 88 528e is original at 350k miles, the car runs great. In over 40 yrs of owning beaters, I had only replaced 2 coils. I dont consider them a wear item.
 
If there is an ignition problem, the coil can puke.
Otherwise, they last a long time [barring infant mortality or physical damage].
Go ahead and change it, but make sure everything else is perfect, first.
 
On our 94 Buick 3800 (now retired), the coils started going out one by one somewhere around 200k miles. I replaced the last of the three at about 250k when the ignition module that sits under the 3 coils, went out. Plugs and wires were always maintained well. Probably should have replaced all three coils when the first one died. Car was totaled at about 268k miles, running like a champ.
 
PandaBear
What car do you have? The longevity of the coil has a lot to do with the maintenance done with spark plugs (correct plug and how often changed) and wires if it has wires (not coil overs). I have a small shop and is very common to have customer come in with miss and check engine light, we see it is missing and find coil bad and plugs have not been changed. Also wrong plugs make a big difference; car calls for iridium plug and people put other plugs in, this will shorten life of coils.
 
Originally Posted By: PandaBear
How long do they usually last? Do they degrade over time and is it possible to diagnose its remaining life?

I'd read somewhere that you should check its resistant at 20C or something like that.


IMHO no, you won't be able to predict a coil's failure until it happens, citing:

a) no 2 vehicles are operating the same environment, temperature, etc.
b)quality issues, etc.

in electronic ignition, coil goes bad usually due to (a) insulation breakdown due to heating cycles on the outer plastic sleeve or the sealant used in the housing, or (b) extremely poor/inconsistent quality control.

It's like the CRT flyback transformer silicone leads: you don't schedule a replacement (predictive?) proactively for no 2 units would fail at a predictable time (some may even outlast the useful service life of the CRT tube; others started to arc in 3 yrs time).

My 2c's worth.

Q.
 
The car is a 95 corolla, has 180k miles, and is on platinum plugs for the last 70k, was on new copper plug every 30k before. Wire was replaced at around 110k as preventive maintenance, it was still running fine other than the rubber shell is hardening. Cap and rotor was replaced on average 30-60k.

All the ignition parts that came out looks decent.

Now that you guys mentioned it, I think having a HG leak on my other car (97 Integra with 210k) and the coolant corroding the spark plug may have something to do with the ignition coil failure. According to my HELM manual, the resistance of the main coil is only 1/2 (or is it 2x, I forgot which way) the new replacement ones I got.

Maybe I should take the coil out of the car and ask the parts counter for a new one, and check the resistance difference to see if it is time to replace? or is it still not a good idea?
 
The resistance checks may be fine, but a small crack can develop in the insulation and will fail under hard use. It can be tough to see.
 
Originally Posted By: rg200amp
180000 miles?? I would replace all the coils. Once my lincoln hits 100K I am replacing all 8 coils.


The nice thing about cars with 1 coil pack per cylinder is that a failed coil won't strand you. You'll get a check engine light, read the OBDII code and find out it translates to "misfire on cylinder 6" or something similar, then drive over to the auto parts place and buy 1 coil. Replace it and you're on the way. Most coil packs are easy to change. for the price of 8 coils packs, you could buy 1 coil and an OBDII reader and probably still save money. Just keep both in the trunk together with a 1/4" socket (or whatever you need to change one) and be on your way.

On the other hand, I wouldn't even worry about it on a car like this, because it won't strand you if it fails.
 
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