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#567807 - 08/04/05 09:43 AM How often should you change the ignition coil?
BlazerLT Offline


Registered: 08/15/04
Posts: 2359
Loc: Canada
How many miles till you should change them. I hear they can get weak over time and don't put out the spark they should.

I was thinking on swapping mine out of my 1995 Blazer with 135,000 miles on it.

I know it is never really mentioned as a maintanence item, but maybe this should be a good practise to get the maximum spark and economy out of our older vehicles?

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#567808 - 08/04/05 01:56 PM Re: How often should you change the ignition coil?
mechtech Offline


Registered: 08/11/04
Posts: 2387
Loc: Chicago area
If there ever was a misfire, full load was put through the coil, and it can break down.
You may get twice as many miles out of it, or it can go next month.
Visually, you can check for carbon tracking, or cracks.

You can check the spark output by cranking the engine and holding a plug wire near a ground. It should be more blue white than yellow. It should jump a half inch .

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#567809 - 08/04/05 02:21 PM Re: How often should you change the ignition coil?
BlazerLT Offline


Registered: 08/15/04
Posts: 2359
Loc: Canada
How can you check for carbon tracking on a coil?

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#567810 - 08/04/05 05:08 PM Re: How often should you change the ignition coil?
TallPaul Offline


Registered: 10/22/03
Posts: 12915
Loc: By Detroit
I changed mine hoping to cure a condition of excess cranking on startup (nothing terrible, but just cranks lonnger than should). It did not help. Worse yet, I bought the coil, installed it, and it would not start. Parts store sold me a dud coil. Anyway it did me no good that I am aware of and cost me around 80$ (better than stock replacement coil).

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#567811 - 08/04/05 05:39 PM Re: How often should you change the ignition coil?
kenw Offline


Registered: 10/10/04
Posts: 1979
Loc: Houston
carbon tracking will look like black cracklines along the surface, usually starting/ending at the HiV outlet 'cup" and going over to a nearby metal ground.

Some of the potted versions will develop separation at the edge of the potting compound, and an arc can exit there.

A simple test for HiV leaks is to run the engine at night, in the dark, (very dark, turn off all the lights!) and look for faint blue arcs. With a wooden stick, move the HiV lead around to see if it will arc when it is close to a metal ground.

Usually a bad coil fails under load (miss, etc) but seems fine at idle, so goose the throttle a bit to load it while you look for those very faint blue arcs.

Please resist the temptation to reach in and touch it with your bare hand.....

This also works for plug wires, in fact, these problems are more often caused by bad wires than bad coils. And bad wires can kill an otherwise good coil.

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#567812 - 08/04/05 08:50 PM Re: How often should you change the ignition coil?
terminaldegree Offline


Registered: 11/09/04
Posts: 365
Loc: western Wisconsin
If you're not misfiring, and the car is running well under high load conditions, I wouldn't mess with them.

If you owned an f-body, you would have replaced all of them at least once by now...

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#567813 - 08/05/05 09:58 AM Re: How often should you change the ignition coil?
cousincletus Offline


Registered: 09/25/02
Posts: 2513
Loc: Richmond, VA
Agree with kenw. GM recommends changing the wires at 60,000 miles. Also use the silicone dielectric grease on the connections. I wouldn't replace what isn't broken.

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#567814 - 08/04/05 10:00 PM Re: How often should you change the ignition coil?
cousincletus Offline


Registered: 09/25/02
Posts: 2513
Loc: Richmond, VA
Don't forget to use premium quality wires. Carquest carries good ones or try www.gmpartsdirect.com.

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#567815 - 08/05/05 02:03 AM Re: How often should you change the ignition coil?
BlazerLT Offline


Registered: 08/15/04
Posts: 2359
Loc: Canada
i'm just wondering id changing the coil which will wear out like any electrical component is a good idea.

My save you more than 80 buck in fuel economy over 2 years or so or even less.

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#567816 - 08/05/05 04:38 AM Re: How often should you change the ignition coil?
cousincletus Offline


Registered: 09/25/02
Posts: 2513
Loc: Richmond, VA
FWIW I had a 1974 Chevy C-10 I sold in 2000 with the original coil. If I replaced I would use genuine GM parts.

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#567817 - 08/05/05 04:56 AM Re: How often should you change the ignition coil?
Gary Allan Offline


Registered: 09/28/02
Posts: 39806
Loc: Pottstown, PA
quote:
A simple test for HiV leaks is to run the engine at night, in the dark, (very dark, turn off all the lights!) and look for faint blue arcs. With a wooden stick, move the HiV lead around to see if it will arc when it is close to a metal ground.
A spray bottle with H2O aids in this. Chain lightning under the hood.

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