Replace all coils or just one

[Lyman]

This is for the Jeep in my sig. So after a plug change I have a bad misfire on cyl #6. COP is bad. Should I just replace the one coil or buy a set? They are all looking old and are pretty brittle after 155k miles. I can get the whole set for ~$150.
Opinions?

 

[Chris142]

Just that bad one

 

[bigt61]

How much do you save on the set? If it's significant, I'd just buy the set and replace them as they fail. If the savings aren't that much, I'd replace the one that went bad.

 

[Lyman]

Originally Posted By: Chris142
Just that bad one
That was my first thought.

 

[Lyman]

Originally Posted By: bigt61
How much do you save on the set? If it's significant, I'd just buy the set and replace them as they fail. If the savings aren't that much, I'd replace the one that went bad.
The savings on a set is $6 each.

 

[Alfred_B]

Originally Posted By: Blkstanger
This is for the Jeep in my sig. So after a plug change I have a bad misfire on cyl #6. COP is bad. Should I just replace the one coil or buy a set? They are all looking old and are pretty brittle after 155k miles. I can get the whole set for ~$150.
Opinions?


I always replace all of mine.

 

[Bottom_Feeder]

If it's a beater, then just one. If it's something you love and rely on, do all of them and keep the good ones for spares.

But before you do that, I assume the COP had to be unplugged from the harness when it was removed. Are you sure that connection was good when you reinstalled it?

 

[Vikas]

Keep a new one in the vehicle along with all the necessary tools to replace it on the side of the road and forget about it.

 

[Lyman]

Originally Posted By: Bottom_Feeder
If it's a beater, then just one. If it's something you love and rely on, do all of them and keep the good ones for spares.

But before you do that, I assume the COP had to be unplugged from the harness when it was removed. Are you sure that connection was good when you reinstalled it?

Connection is good. This Jeep is far from a beater. I drive it 50+ miles a day and it otherwise runs like a top. Drives like new.

 

[Bgallagher]

Originally Posted By: Blkstanger
Originally Posted By: Bottom_Feeder
If it's a beater, then just one. If it's something you love and rely on, do all of them and keep the good ones for spares.

But before you do that, I assume the COP had to be unplugged from the harness when it was removed. Are you sure that connection was good when you reinstalled it?

Connection is good. This Jeep is far from a beater. I drive it 50+ miles a day and it otherwise runs like a top. Drives like new.


If that is the case I would replace all of them. Easier to do the whole job at once versus waiting for each to possibly fail and replace one at a time.

 

[Trav]

Fix it once and fix it right, replace all of them. You say its not a beater and you drive it a lot, don't frig around.
A bad coil doesn't do the expensive cat any favors and could cost more in the long run.

 

[zzyzzx]

I would replace the whole set, but just do the bad one first and drive it like that for a week, just to make sure.

 

[Lyman]

Thanks guys. I decided to do the whole set. I am planning a 1500 mile trip in June and don't need any future head aches.

 

[Kuato]

Originally Posted By: Blkstanger
Originally Posted By: Bottom_Feeder
.... do all of them and keep the good ones for spares.


Connection is good. This Jeep is far from a beater. I drive it 50+ miles a day and it otherwise runs like a top. Drives like new.


My thought also - replace all so you won't have several bad ones and one good one....especially since it's the daily driver.

 

[demarpaint]

Originally Posted By: Blkstanger
Thanks guys. I decided to do the whole set. I am planning a 1500 mile trip in June and don't need any future head aches.


Smart move!

 

[MNgopher]

I've gone the other route and done 1 at a time on my '04 F150. To date, 5 of them have been replaced between 85,000 miles and 182,000 miles. At nearly $50 a crack, a full swap would've been $400. Every failure has been the same - a series of small misfires shows up under light acceleration between 40 -and 50 mph. The shuddering can linger for months before it will ever set a code, but using torque pro I can pull the misfire counts. Since I am now a beater mode, happy with my choice to piecemeal it...

(My '07 Explorer uses the same coils, and to date has had one replaced at 115,000 miles).

 

[Kool1]

Whether you replace one coil or all of them, make sure you get high quality replacements or OEM coils. I've seen numerous aftermarket coils fail right out of the box or fail within a short amount of time after installation.

 

[Lolvoguy]

Originally Posted By: MNgopher
Every failure has been the same - a series of small misfires shows up under light acceleration between 40 -and 50 mph. The shuddering can linger for months before it will ever set a code


Is this common to all vehicles? ON my DD focus after changing the plugs I get the same unevenness when using light acceleration. Also at about the same speed

 

[ARCOgraphite]

Are they OE quality? - otherwise they may have poor life and 2 of the 8 will probably not work at all. That's my luck hopefully not yours

 

[ARCOgraphite]

Doing a plug change is more involved then removing old plugs and twisting in the new ones. There are many tricks to make sure high voltage secondary keeps the spark going into the hole. Over 40 years of doing precision tunes teaches you something - if you're willing.