Coil & Spark Plug Repair Advice

Greetings All First Gen Folks,
Long time listener, first time caller. 2003 RCLB SR5 4X4 with the 2UZ-FE that just hit 151k miles. Fully stock short of a Champion radiator and 3rd gen 4Runner LTD rims. At 138k, timing belt service (Aisin kit with idler bearing & hydraulic tensioner), valve cover gaskets, cam/crankshaft oil seals. New OEM water pump, thermostat and drive belt. New spark plugs but left the original Denso coils.

Highway driving this week and hear a noise. Check engine light starts flashing. Get off the highway and am close to home so limp back. Code is P0302, 2nd cylinder misfire. At first I think I'll pull the coil from 2 and swap with 4 to see if it's the coil or the spark plug, but open up 2 and find both the coil and spark plug in terrible condition. Coil is fouled and burnt? And the spark plug in pieces. Hoping to learn from all of the first gen experts here about next steps:

Can I safely extract the partial spark plug myself? Is there a risk of particles getting into the chamber?
Is the burnt coil and broken spark plug a sign of a bigger issue I'm not recognizing?

There are a few extenuating circumstances I should add, as I'm unsure if they could have also played a factor?
I had just changed the oil. Was a total idiot and left the oil cap off during that drive. Zero oil escaped.
I added two bottles of red Heet to a 1/4 full tank, but hadn't made it to the gas station to fill the rest of the tank up.
The right catalytic converter was stolen and hasn't been replaced yet. Been driving for a couple months with delete right it till I can find an OEM or replacement that won't code.

Really appreciate all the knowledge and support here about arguably the best first generation truck ever produced. Great community I hope I can add to the conversation. Thanks all for your time and consideration.


Dave

 

For the plug, use small air tips (sold for detailing or fine cleaning) and a shop vac to get the large pieces out. Then follow up with an air compressor with an air gun/nozzle to blow the smaller stuff out (wear eye protection).

 

I do have a question, you just did a lot of maintenance, did any of it involve new ignition parts, like coils?

When you swapped the plugs, did you 'foul up' and use anti-seize on the threads?

Where'd you source your parts from?

 

Hi Shifty.
Thanks for your help. I didn't personally do all that work at 138k, my apologies if I misrepresented myself. I know just enough to get me into trouble, but do take great satisfaction in asking/framing the right questions to find a resolution to the issue. I'm also a super worrywort and always fear the worst, so I always want to look at a problem from all sides before reacting. Plus where I am, shops are so far out in service. That P0302 looked easy enough to diagnose, but when I opened up that #2 and saw the burnt coil and broken plug I knew I needed even more experience to diagnose. Really appreciate you chiming in as all the expert advice you've given folks here is one of the biggest reasons I came to purchase this RCLB.

It was actually the previous owner who had all the work at 138k done through a local shop that comes highly regarded. So I can't speak to if anti-seize was used on the plugs. Hoping that they weren't though. He purchased the timing belt kit himself through RockAuto, the seals were also OEM through the dealership. The coils appear to be the stock OEM, and I didn't see them invoiced on any of the paperwork with the truck.

Thanks Again,
Dave

 

I mean, the reality is, the coils on these trucks are notorious for cracking at the sleeves with time and heat. They put out quite a hell of a charge to boot.

There's a solid chance the sleeve gave way and started arc'ing to the tube, melting the plastics and essentially electrically exploding the spark plug. I wouldn't make it out to be anything bigger than that. I'd expect to see more char in the spark plug tube, but electricity will absolutely blow things apart.

If it were me, and I were in your shoes, I would take corrective actions to solve the problem at hand:

• Get a new OEM (Denso) coil pack for that cylinder, from a reputable source.
• Proactively change all spark plugs with the recommended Denso or NGK part number in the 2003 owner's manual, from a reputable source.

This does a few things:

• Solves your destroyed coil problem
• Gives you a new maintenance baseline for the spark plugs, and rules out any possibility the previous owner used substandard or fake plugs
• Should allow the system time to burp up any other codes related.
• Lets you assure the plugs are gapped (if applicable) and not installed with anti-seize or similar lubricant

I could've sworn I saw another reply in here, someone pointing out that the spark plug tube gasket on that cylinder was smooshing out, but I'm not sure it's the case. I see the exploded coil pack is missing part of its seal, and I think that's a piece of seal stuck in the gap between the spark plug tube and the valve cover. Clean that up.

And is that traces of oil I see on the valve cover?

 

Genuine Denso coil pack and a full set of their plugs for sure. Having my own baseline will be reassuring too. Won’t be able to pull them till the weekend but curious what comes out. I also think the rubber is the remains of that coil pack seal. It crumbled away during extraction and I haven’t tidied up in that picture. Taking assassin’s advice and sucking and blowing to get everything out.


Fingers x’ed that oil spot is just from the drive with the cap off. It may have even been from the cap rattling around, as I had to procure a new one. Know more when I dig in Saturday.

Thanks everyone for all the expert advice and encouragement.


Dave

 

Hard to tell from the pics, but I'm wondering if the spark plug failed first, allowing combustion gas to enter the tube, melting the coil. If the coil failed first, it would likely just arc to the tube leaving the spark plug out of the equation entirely.

Edit: it would be interesting to see what the rest of the spark plug looks like once it's extracted.

 

Hi OP curious if you have any updates o this. Also have you been able to locate any OEM coil packs? The (excellent) Toyota parts website shows it as “unavailable” without any more details. Thx

 

Denso coils from rockauto are exactly as original equipment. So much so you can see where they grind off Toyota to just sell them as Denso.

 

Awesome thanks for the info.

 

Just make sure you don't buy on scAmazon or fleaBay, you'll likely end up with fakes. More info over here.

@PNW_RCLB where did you end up landing on this, just curious?

 

I saw someone use dirty deeds injectors on a 1st gen but I honestly don’t know anymore than that.

 

In my experience ngk and Delphi work fine but it affects the pitch at startup in a way I don’t like. Had to replace all 8 ( previous three owners appeared to have not replaced them, last spark plug replacement in 2011) but could only source two densos locally. Going to do boot kits on some junkyard pulls, clean em up, and will have a nice set of spares