Ignition coil

2000 Honda Accord. I’ve been told I have a bad ignition coil. Do I need to replace all six or can I just replace the one? Thanks.

If it were my car, I’d just replace the bad one and expect to possibly have to do it to the other five one at a time as they go bad as well.

They are individually replaceable.

I’d replace them all and get it over with. The car is (pushing) 16 years old, and coils have pretty consistent operating hour lives. Usually if one goes on an old engine the others aren’t far behind.

Are we talking about individual Coil Over Plug (COP) coils? I’ve never owned a Honda car, but I’ve sure replaced individual coils on MANY others with good results for many thousands of additional miles. If money is no object, by all means replace all six. If not, one should get you down the road for long way, especially if it’s on the front of the engine where the labor is minimal.

You can certainly replace just one. Whether that’s a wise choice is up to you.

Back in January I had a 2000 Toyota come in, customer stated truck was running very poorly and engine light was on. We found coils #3 and #8 failing. I told the customer the car needed 2 coils and a set of spark plugs, and I recommended the remaining 6 based on similar age and service life. Earlier this week the truck was back, running poorly and engine light on. This time coil #5 failed. Needed a coil and spark plug, recommended the remaining 5 coils as well. I offered to do the other 5 coils at no labor charge since we were in there anyway. Customer declined the additional coils.

Now knowing that every time the car comes in with a misfire and engine light, he’s going to pay a $96 diagnostic charge to find the trouble, I think it would have made sense to buy 5 more coils at $72 each and be done with it. But he wanted to gamble. So 6 months from now when one goes bad I’ll make more money replacing just one for $200 when he could have done 5 more this week for $360.

just replace the one bad coil. However realize that if one 15 year old coil is bad, then others might go bad as well. If you have a 2nd coil go bad in the next 12 months then I’d consider replacing the whole bunch. The coil part is expensive, but access is easy so replacing them is easy. If you have any mechanical skill at all, this is an easy DIY job.

You should also be aware that coils can fail due to high miles spark plugs or some fault which affects those plugs, moisture in the plug boots and wells, etc.

Agreeing w/ @ok4450 … worn spark plugs, or even the gap growing too wide, can damage the coil. So don’t put a new coil in an engine with worn spark plugs, otherwise you risk damaging the new coil.

There are no moving parts in a coil. In theory, they should last forever, but plastics used in their manufacture can break down due to age. Excess heat from misfiring plugs usually is what damages them.

I replaced all four in my Olds but because they had a history of burning coils up.

To stray a little, I was out mulching leaves tonight with the riding mower to keep them from blowing in the neighbors yard, and all of a sudden the mower just quit like turning the key off. It has been running great and just all of a sudden. I’m going to replace the coil since it shows no or very weak spark and does not pop with starting fluid so hope that’s what it is. But guess the transistors can just quit with no warning. Coils can be a little unpredictable.

When one coil gives up the ghost…the rest are not too far behind. I’d replace them all.

I should amend what I said: If the bad coil is on the back side of the engine where it’s a pain in the butt to get to on that car, I’d replace the 3 plugs on that side to save myself the trouble of doing that job more than once. If it’s on the front side, I’d replace just the one.

They do sell 3-packs for your car for exactly that reason.

The insulation on coil windings is a polyamide-imide coating applied like a varnish. It’s an excellent product for the application, but it has a different thermal expansion coefficient than the copper wire, has low elasticity, and over extended time and thermal cycling it begins to fracture. When it does, the winding can begin to short. This is a candidate particularly with coil, solenoid, or motors failures wherein heat is a factor, as it so often is in engine compartments.

The good news is that this is an excellent coating for these applications, robust, tough, and consistent, and the process is extremely consistent and easily tightly controlled.

This extreme consistency also makes the lifespan of “sets” of products from the same manufacturing process typically very close to one another. Variations in environment, such as one set of plugs being on a rear bank more exposed to exhaust heat and less well ventilated than a set on the front bank, can cause variations in lifespan, but typically not greatly.

My personal philosophy is that a failure on a new engine is likely an anomaly, perhaps an “infant mortality”, but on a 15 ear old buggy it’s prudent to just change them all while you’re there.

Somebody told me that a good place to obtain a length of coil wire with the varnish already applied as described by TSM above is from the base of burned out CFL light bulbs. I’m not sure how you’d do that though. It seems sort of dangerous.

I have a coil related lawnmower story @Bing . I had this old decrepit looking rotary 2 cycle gasoline engine Lawnboy (or maybe LawnGenie, forget) push-type lawnmower for like 20 years, and used it every week mowing 1/3 acre of uneven and steep grade, lawn and weeds. It was flawless, just kept on working. I could hit a rock, it would stall. One pull, it would start up again like nothing happened. Until one day it didn’t.

So I took it apart, the piston rings were shot, maybe 1 mm left. I tried to remove one ring, it crumpled away into a dozen pieces. No worries, I bought some new rings. Again, it started the first pull ran about 30 minutes, then stopped again. This time the diagnosis was easy. The coil had a big crack in the casing.

$50 and it runs great again. I guess not bad for 560 hours on it. I don’t use CFLs at all, just LEDs. I don’t like the mercury in them or the fire hazard but they have to be turned in as hazardous waste and you can’t take them apart without calling i the hazmat team for a clean-up.

I agree with you regarding the mercury vapor. The government’s push to get people to switch from incandescent bulbs to CFLs to save the environment is beyond puzzling. There are 250 million ++ households in the U.S. Imagine if you will every one of them throwing away ten lightbulbs a year. Subtract the 10% that MIGHT be disposed of as HAZMAT (my estimate is generous) and add up the mercury. IMHO it’s another example of bad regulation.

Would have been smarter to require quartz-halogen capsules inside standard size bulbs.

That would double life and boost efficiency 30-80% over standard incandescent.

I consider fluorescent lighting in the same category as vacuum tube electronics: obsolete and best avoided for most applications.

I’ve become a real fan of LEDs once you get over the initial price. Of course some bulbs are just not available yet like the decorator ones, but the standard 60 and 100 watt and the recessed look just the same as standard and I’ll probably never have to replace them myself. I’ve only done the ones that are on a lot like the kitchen, hall, living room, office, etc. Last winter I tested a light outside to see if it still worked when it was 10 below and no problems, so I use them outside now too. I’ve still got a gross of 60s and 100s in stock though that may become obsolete.

I've become a real fan of LEDs once you get over the initial price.

They’ve dropped a lot in price. They’re 1/10 the price they were just a few years ago. I think all the bulbs we could replace with LEDs have been.