Spark plug and ignition coil question

[atalarico]

Hey all,

Just changed out the plugs on my 2004 V8 (using Denso long-life's again) and I noticed a few things:

1.) Almost all of them looked dirty like this. Bad sign or just a sign that they probably haven't been changed (156k on the odometer)?

2.) I noticed one of the ignition coils is cracking. Replace that ASAP or what?

3.) I also noticed that a couple of the ignition coils had what appeared to be oil speckles on them. Bad thing?

 

[Prommy]

How does the spark plug from the cracked coil look? A failed/failing coil pack can cause misfires, which could lead to increased deposits on the plug. If you have the ability to scan for misfires, you should check that cylinder. If you don't SEEM to be experiencing problems, I'd look to replace it as is convenient. If this engine works like others I've worked on, keep it off the #1 cylinder, as it's firing reliability affects the others.

Dark deposits on the plugs could be indicative of rich mixture (especially if it's all plugs showing fouling) or oil getting into the cylinders (especially if it's one/a few spark plugs showing fouling). This isn't enough to throw warning flags, but it enough that I'd look into it. Could just be grime that works its way in, could be early indicator of a problem.

How to diagnose? Track the O2 sensors and fuel air mixture to see if the engine is running more rich than spec. Could be MAF or O2 sensor issue. A cylinder compression test is pretty easy to do (my autoparts store "rents" the tools to do this).

Other than that, make sure your air filter is clean.

 

[Prommy]

For the record, from solely the one picture, the plug doesn't look truly awful. I wouldn't go throwing money at a problem that might not exist.

 

[AuSeeker]

Hey all,

Just changed out the plugs on my 2004 V8 (using Denso long-life's again) and I noticed a few things:

1.) Almost all of them looked dirty like this. Bad sign or just a sign that they probably haven't been changed (156k on the odometer)?

2.) I noticed one of the ignition coils is cracking. Replace that ASAP or what?

3.) I also noticed that a couple of the ignition coils had what appeared to be oil speckles on them. Bad thing?

How does the spark plug from the cracked coil look? A failed/failing coil pack can cause misfires, which could lead to increased deposits on the plug. If you have the ability to scan for misfires, you should check that cylinder. If you don't SEEM to be experiencing problems, I'd look to replace it as is convenient. If this engine works like others I've worked on, keep it off the #1 cylinder, as it's firing reliability affects the others.

Dark deposits on the plugs could be indicative of rich mixture (especially if it's all plugs showing fouling) or oil getting into the cylinders (especially if it's one/a few spark plugs showing fouling). This isn't enough to throw warning flags, but it enough that I'd look into it. Could just be grime that works its way in, could be early indicator of a problem.

How to diagnose? Track the O2 sensors and fuel air mixture to see if the engine is running more rich than spec. Could be MAF or O2 sensor issue. A cylinder compression test is pretty easy to do (my autoparts store "rents" the tools to do this).

Other than that, make sure your air filter is clean.

Deposits/fouling on plugs that are an issue on how the combustion process is doing would show up on the insulator not the threads, in this case the insulator looks as white as the new plug, almost all plugs that have been installed for a while will have "deposits" on the threads, which is what I see on the OP plug threads, this can be either carbon, oil staining, both of which is sorta normal for the most part it could also be some kind of anti-sieze that someone used the last time the plugs were changed, if they're not the orginals, if they're the orginals then the thread deposits are more than normal for the amount of miles mentioned.

If it's carbon which I believe it is, the seal to the head is the crush washer and as such carbon can get into the thread area of the plugs, if it's oil then there maybe a small leak where the valve cover seals around the plug areas, unless you're using oil it shouldn't be a big concern, BUT I would check all the valve cover bolts to see if they're tighten properly, I check mine everytime I change the plugs because they as well as any bolts on your vehicle can loosen a bit over time, especially the smaller bolts that require less torque values.

OP, were the plugs on both banks the same brand?

If so they are not the original plugs, if they are different brands then they are the originals plugs, this is just the way Toyota did it, the story I have read is that the heads came from 2 different factories and they had different brand plugs at these factories, both brands are good brands and approved by Toyota.

 

[atalarico]

OP, were the plugs on both banks the same brand?

I'm ~90% sure they were the same brand, but unfortunately the garbage already got collected so I can't go dig them up to check. I guess that means they were changed at some point then, and I think the numbers from the new plugs to the old plugs matched. I guess I just threw away money on plugs I guess since they'd be long-life iridium's too? Ah well, at least I know their age now.

Thanks for the other input too! I'm going to lightly snug up the valve cover bolts just in case. If I find one or two that are loose then I'll know the most likely culprit. I replaced the valve cover gasket and spark plug seals in my 3rd gen (twice...yay) so while I'm not looking forward to doing that again, I guess I can if I have to.

How does the spark plug from the cracked coil look? A failed/failing coil pack can cause misfires, which could lead to increased deposits on the plug. If you have the ability to scan for misfires, you should check that cylinder. If you don't SEEM to be experiencing problems, I'd look to replace it as is convenient. If this engine works like others I've worked on, keep it off the #1 cylinder, as it's firing reliability affects the others.

Dark deposits on the plugs could be indicative of rich mixture (especially if it's all plugs showing fouling) or oil getting into the cylinders (especially if it's one/a few spark plugs showing fouling). This isn't enough to throw warning flags, but it enough that I'd look into it. Could just be grime that works its way in, could be early indicator of a problem.

How to diagnose? Track the O2 sensors and fuel air mixture to see if the engine is running more rich than spec. Could be MAF or O2 sensor issue. A cylinder compression test is pretty easy to do (my autoparts store "rents" the tools to do this).

Other than that, make sure your air filter is clean.

The engine seems to run fine to me but I think anything would feel fine coming from a 3rd gen V6?

It was from one of the back two cylinders on the driver's side, either 7 or 5. #1 looked fine though, so that's good for the rest of them behind it. As for the condition of the plug from that cylinder, it looked the worst of the bunch and I'm pretty sure it's the one I took the picture of, so it's a little more fouled than the rest but not drastically so since they all were about that level of dirty.

Air filter is good to go though so that's not the culprit either.

For the record, from solely the one picture, the plug doesn't look truly awful. I wouldn't go throwing money at a problem that might not exist.

Thanks! I'll keep an eye on things but sounds like it's par the course for plugs of an unknown, but probably older, age.

 

[blackoutt]

Plugs look good for the mileage (at least that one pic). I'd replace that coil pack with OEM asap so it doesn't leave you stranded but run it until new parts comes in if it's not causing any issues. No concern about the splatter staining on the other coils, stains do not affect their performance. Just be sure all the coil pack to valve cover seals are intact and clean on reinstall. Plugs torqued to spec.

 

[atalarico]

Plugs look good for the mileage (at least that one pic). I'd replace that coil pack with OEM asap so it doesn't leave you stranded but run it until new parts comes in if it's not causing any issues. No concern about the splatter staining on the other coils, stains do not affect their performance. Just be sure all the coil pack to valve cover seals are intact and clean on reinstall. Plugs torqued to spec.

Thanks! That was the worst looking plug I think of the bunch, so they were varying degrees of that or less.

I'll get a new coil pack ordered up from either Camelback or Amayama then. Edited to add: just checked around and CB has them for $85+shipping while RockAuto has this DENSO 6731303 {#9008019027} Coil on Plug DENSO is the OE supplier for this vehicle" for $51 + shipping. WTF? Is that one at Rock the real OEM one then as it says?

Are the seals the little rubber grommet things at the top of the coil pack that come off with them? If so, I removed all of them and wiped them down with some silicone spray and reinstalled them. They were all pretty spongy and rubbery, so if they're supposed to be firmer than that maybe I should get some new ones.

Plugs were all torqued back to 15ft/lbs with a torque wrench (at some clever angles for the back driver's side one too).

Thanks for the sanity check!

 

[blackoutt]

Thanks! That was the worst looking plug I think of the bunch, so they were varying degrees of that or less.

I'll get a new coil pack ordered up from either Camelback or Amayama then. Edited to add: just checked around and CB has them for $85+shipping while RockAuto has this DENSO 6731303 {#9008019027} Coil on Plug DENSO is the OE supplier for this vehicle" for $51 + shipping. WTF? Is that one at Rock the real OEM one then as it says?

Are the seals the little rubber grommet things at the top of the coil pack that come off with them? If so, I removed all of them and wiped them down with some silicone spray and reinstalled them. They were all pretty spongy and rubbery, so if they're supposed to be firmer than that maybe I should get some new ones.

Plugs were all torqued back to 15ft/lbs with a torque wrench (at some clever angles for the back driver's side one too).

Thanks for the sanity check!

Denso should be fine. I'm a believer in OEM parts but if we know that they are from same manufacturer and just not Toyota branded that's okay too!

The seals are supposed to be soft as described to take up and irregularities in the sealing surface, vibration, expansion/contraction etc. Sounds like you're fine. Good work!

 

[damthemainstream]

Denso should be fine. I'm a believer in OEM parts but if we know that they are from same manufacturer and just not Toyota branded that's okay too!

The seals are supposed to be soft as described to take up and irregularities in the sealing surface, vibration, expansion/contraction etc. Sounds like you're fine. Good work!

Not to be pedantic, but OEM (Original Equipment Manufacturer) would refer to someone like Denso, who was a manufacturer of original equipment for Toyota. The part would come in Denso packaging with a Denso part number. OE (Original Equipment) would refer to that same identical part, but in Toyota packaging with a Toyota part number.

 

[blackoutt]

Not to be pedantic, but OEM (Original Equipment Manufacturer) would refer to someone like Denso, who was a manufacturer of original equipment for Toyota. The part would come in Denso packaging with a Denso part number. OE (Original Equipment) would refer to that same identical part, but in Toyota packaging with a Toyota part number.

I agree with how it should be as you state but there's too many "OE" and "OEM specification" parts out there that are complete garbage. To clarify then, I am a believer in Toyota branded parts, then next comes the same part from the same manufacturer without the Toyota branding. Ignition components are one of those odd ones where we very easily know the manufacture, I'm assuming something about initial agreements with the supplier for non-compete clause and all that, whereas a lot of other parts have no manufacturer branding.

 

[atalarico]

I've also learned my lesson on buying non-OEM parts before when my NAPA 555 brand LBJs crapped the bed with less than 25k on them. It's a good thing I replaced them with OEM ones because I totaled my 3rd gen like 5k miles after that. Oh and the newer OEM ITR and OTRE's I put on around that time too. damn I miss that truck. =(

But really, I think the Denso brand OE ones are good to go for sure.

 

[atalarico]

So I finally replaced the cracked coil today. I *lightly* snugged up my valve cover bolts as some were kinda loose, and I pulled the other ignition coils to check them out. Here's what I found.

Two of them had splits along what appears to just be a normal seam. Anything to worry about?

(this one is the longest...)

(hard to see but it's just in the center there)

And then one has tiny cracks forming not on any seam and looks a lot like a less severe version of the one I just replaced.

Should I worry about any of them? That's about $150 in parts if so. =/

 

[BackOff]

Seems like as I pull stuff apart I break more of the plastic items...as it ages...pushing 15 years...plastic seems to break down.

Throw a code ... then fix it ... or fix it before it leaves you on the side of the road, in the dark, 150 miles from home...all up to you.

 

[AuSeeker]

So I finally replaced the cracked coil today. I *lightly* snugged up my valve cover bolts as some were kinda loose, and I pulled the other ignition coils to check them out. Here's what I found.

Two of them had splits along what appears to just be a normal seam. Anything to worry about?

(this one is the longest...)

(hard to see but it's just in the center there)

And then one has tiny cracks forming not on any seam and looks a lot like a less severe version of the one I just replaced.

Should I worry about any of them? That's about $150 in parts if so. =/

If it were me I would replace them but if it's running OK and spending the money now to replace them would be a hardship I would drive it as is BUT start saving a little bit each week until you save up the money and then replace them all at once and get it over with, the peace of mind alone would be worth the money spent replacing them, just don't put it off for a long time because you never know when it could/would become a major issue at a bad time.

 

[atalarico]

If it were me I would replace them but if it's running OK and spending the money now to replace them would be a hardship I would drive it as is BUT start saving a little bit each week until you save up the money and then replace them all at once and get it over with, the peace of mind alone would be worth the money spent replacing them, just don't put it off for a long time because you never know when it could/would become a major issue at a bad time.

Thanks. I'll take $150 from the tire fund and redirect it I guess. Just another setback to getting new shoes before the wheeling season starts. =( I know I know, new tires will look really pretty on my truck...10 miles from the trailhead when one of those ignition coils craps out.

 

[Cornellrpg]

Hey all,

Just changed out the plugs on my 2004 V8 (using Denso long-life's again) and I noticed a few things:

1.) Almost all of them looked dirty like this. Bad sign or just a sign that they probably haven't been changed (156k on the odometer)?

2.) I noticed one of the ignition coils is cracking. Replace that ASAP or what?

3.) I also noticed that a couple of the ignition coils had what appeared to be oil speckles on them. Bad thing?

If my plugs are the same. Raplacing the will increase mileage?
Im having a very low mileage on my car and would like to know if doing this will help me or not. As no issues with misfires or rough idle.

 

[Karnivor707]

My 4runner was sold to me and had period check engine light on and was throwing misfire codes from multiple cylinders, previous owner had put new spark plugs but that didn’t fix it. I Changed all 8 coil packs and spark plugs and now no check engine lights, and engine running smoother than ever . I was expecting an increase in mpg but it seems about the same and now decreased with my lift and 33” tires. But I will say this 4.7 runs smooth as hell and is a pleasure to drive.

I found some coil packs for a gx470 on eBay brand new I think around $60 shipped and found some that had a 5 year warranty. They seem to be working good. These are the same ones I got Set of 8 Ignition Coil on Plug Coils Pack For Lexus GS430 LS430 Toyota UF230 602105725392 | eBay