When to replace Ignition coils.

[Hokie LX]

I’m debating replacing all 8 coils in my truck. I may be in my head but I feel like she’s down on power and getting worse mileage over the past few months than she was before. Plugs were changed 10k miles ago and all else is up to date maintenance wise except for the coils and at 193k I think they’re original.

 

[dustbowl]

i replaced all eight. but i read an article that said coils don't get weak they just fail. although the same article suggests that the insulating boots do go bad and allow voltage leaks that can mimick a weak coil. i would suggest try replacing the boots and see if that helps. i wish i had gone this route just to see if it improves performance. i might just try it on one of my other 2uzfe engines.

 

[2001LC]

It's ture bad boots can be issues. But they're easy to spot.

Also if you review some of the videos in this thread on testing coils. You'll see in OP a video that is suggest they do weaken. As does a more recent video using differ test equipment.

I can say, that I just found one going bad. Not actually bad, but it did misfire "underload only". It looked like new:

1. No discoloration from heat.
2. The boot soft and tight as new.
3. No sign at all it could be a bad coil.
4. It did not throw a code.
5. All coil where good looking and all boots good.

But I felt idle and acceleration could be improved. Replace all 8 did improve those and reduced fuel smell!

 

[Rolocado]

It's ture bad boots can be issues. But they're easy to spot.

Also if you review some of the videos in this thread on testing coils. You'll see in OP a video that is suggest they do weaken. As does a more recent video using differ test equipment.

I can say, that I just found one going bad. Not actually bad, but it did misfire "underload only". It looked like new:

1. No discoloration from heat.
2. The boot soft and tight as new.
3. No sign at all it could be a bad coil.
4. It did not throw a code.
5. All coil where good looking and all boots good.

But I felt idle and acceleration could be improved. Replace all 8 did improve those and reduced fuel smell!

When I was replacing my plugs, I blew out the plug holes with canned air before I removed them as to theoretically not let any debris into the cylinders. Was that a poor choice and is there any way debris could have gotten in outside the spark plug tubes?

 

[dustbowl]

cleanliness is next to Godliness. i doubt there would be anything in the tubes that would hurt anyway.

 

[2001LC]

When I was replacing my plugs, I blew out the plug holes with canned air before I removed them as to theoretically not let any debris into the cylinders. Was that a poor choice and is there any way debris could have gotten in outside the spark plug tubes?

You're find, since plugs where in at the time.

 

[firewood]

Someone will probably snatch these up before I can, but are these legit?

GENUINE OEM NEW 90919-02230 Toyota Lexus Ignition Coil | eBay

 

[firewood]

OK, answered my own question with this thread: Need help identifying genuine Denso 90919-02230 coil packs from fakes

Search still works!

 

[jlm43]

Well this box just showed up so for me, it’s going to be soon. I’m not getting any codes but there are times when it idles a little rough. I don’t think it’s anything major but since the truck is still relatively new to me, I’m being a little hypersensitive to every little noise or rumble. It’s currently at 137,500 miles and my paranoia is setting in so I figured I would just do all 8.

 

[Mike6158]

I had one go out around 190,000. I replaced it. About 20,000 later I bought 8 OEM's and replaced them all. I don't expect to need to change them again. I have a post where I gave away the working older coils. Just asked for shipping. They went fast.

 

[white_lx]

Anyone ever used a Waekon / Hickock coil-over-plug tester on these vehicles? Just curious if it can be used do diagnose weak coilpacks by setting the sensitivity to a known good coilpack and then determine which coilpack(s) is/are below that threshold. Could be the bee's knees, if it works as advertised.

https://www.amazon.com/Waekon-76562...1536176281&sr=8-1-fkmr0&keywords=Hickok+76562

Another option would be the Lisle 20700 coil on spark tester (or any device with adjustable gap) and check the maximum gap it will spark. Fuel injector would need to be disconnected otherwise you flood the cylinder.

https://www.amazon.com/Lisle-20700-Coil-Spark-Tester/dp/B00IXMA1RY

Is there enough difference in arcing distance to distinguish between a good and a marginal coil pack that does not throw codes yet?

 

[eurodre]

Anyone having any stuttering issues after replacing their coils? It seems like if I don't have the brake pedal all the way down the lx just wants to keep going forward like it's antsy to drive

 

[firewood]

I replaced all of mine this summer when I did the valve gaskets, haven't had that problem (LC). Man I love the sound of that thing firing up.

 

[Wilsil]

Have a rough running engine for a week. Stuttering when under load so I dropped it off at the mechanic.
He couldn't find a code on the different scan tools he used but he said that it was misfiring.
No CEL coming up.
Last Saturday I replaced all 8 spark plugs (were in the car for 80,000 kms) and noticed the ignition coils of #1, #2 and #8 had a cracked housing.
My local car store had 1 Bosch and I order 2 other Bosch coils through ebay which should arrive today.
I installed the new one in #1 but no change.
The picture shows the crack.

 

[Wilsil]

Replaced the other 2 ignition coils yesterday.
No change.

 

[2001LC]

Try 8 new Denso

 

[Wilsil]

What is wrong with original Bosch?

 

[GTV]

I never gave coils a thought before I did the plugs on my new-to-me 259k mile Sequoia a few weeks ago. They look like they could be originals but who knows, truck seems to be running fine.
I’m certain that my 247k mile Tundra has the original coils (I’ve owned it 14 years), and it does occasionally have a stumble. Wondering if this could be the cause...

Has anyone tried that coil test tool a page or two back? If accurate, that would be a valuable tool.

 

[2001LC]

Bosch was once (40 years ago) a very good name. Today I'd only use Denso coils (COP).

The test equipment in OP second video would be nice to have. It would give indication of weak coils, those not throwing a CEL.

I've twice had indications of weak coils. These are coils still within spec as they fire well enough most of the time, so that they don't set off the CEl or even a pending code.

In one case I'd get a misfire only under load. This was detectable in tech stream as to which coil, by holding brake on while in D and raising RPM.

Another would run fine in above test and no indication in tech stream at any running condition. But when flooring the gas pedal while getting on the HWY, the acceleration wasn't as smooth as it should be. A new set of Denso clear it up.

In both above examples the engine was well tuned. That is; new intake manifold & T-body gaskets, new vacuum lines, new Denso spark plugs, MAF sensor clean, cam/crank and o2 sensors all good, tested/clean/rebuilt or new fuel injectors, new FPR, etc... It was new Denso coils that took it over the top to smooth acceleration!

Also worth a note: it is well worth getting a Denso coil boot kit, when stiffness is felt in rubber of boots.

When coils are found cracked, it's likely they ran hot. It's a good bet the engine ran with spark plugs loose or a wide gap or both. In either case the spark plug will draw excessive current from coil. This produces excessive heat, which is enemy of COPs.

 

[dnp]

Try 8 new Denso

^^THIS^^ Bosch doesn't seem to play well in anything in which they weren't specified as OEM. Not sure why, but that just seems to be the case. Their O2 sensors seem to be about the worst offenders in that category.....