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Discussion Starter · #1 ·
So I have a BIG problem. I should first mention that the spark plugs have never been changed under my ownership (3 and half years/ 20,000 miles) and I don't know the last time the previous owner changed them.

I was driving last night to run some errands. After my first trip I started up the car and the exhaust starts popping in neutral and I thought that this was very funny, maybe cold weather or dity MAFS. So I think nothing of it. Then after after a few more errands the engine starts to 'chatter' a little more when accelerating and I get a CEL. I stopped for a bit, popped the hood and could smell fuel. I drove to an Autozone a few blocks away and got the CEL pulled, I was told it was a misfire on Cylinder 4 and that it's okay to drive around like this because it's most likely just a bad spark plug. The exhaust continued to pop in idle and the engine began to knock a little louder when accelerating.

So I tried to find a Denso plug(s) to replace it with but the only place that had them was closed. Taking the advice of the Autozone employee and another friend who knows Celicas quite well, I decided to keep driving it. I drove another 5-6 miles and stopped at a friend's place. After a couple hours I tried to make it home but my problem got REALLY bad. The knocking was even louder and my acceleration was studdering. The engine noise got too loud and I was no longer making any power basically so I had to pull over. Eventually, the engine was even popping almost like a go-kart.

The next day I checked everything out. My coil in cylinder 4 was demolished, roasted. The lower rubber section is completely missing and it's cracked along the side. The spark plug is in the same condition, being burnt black and missing areas of white thread-like looking material above the 'real thread'. It looks like its vertically smushed too. I pulled some pieces out of the hole but not enough to put together the rest of the spark plug and I found no remains of the coil. This is what it looked like, black marks surrounding the hole.










Coil:







Spark plug:









When I went to remove the spark plug it was loose and could be wiggled. I didn't even have to twist it to get it to come out. I just had to lift up. I got new spark plugs and an ignition coil from an 03 Matrix, tried replacing them but I found out that I can't even get the spark plug to grab the thread in cylinder 4. So I don't know if the thread has been stripped or what.

Cylinders 1-3 are fine, the spark plugs are worn but have been replaced and the coils are fine. I'm getting it towed to a shop today but I was just curious if there may be significant damage? besides not being able to get the spark plug to screw in. Where could the rest of the coil and spark plug dissappeared to? Just burnt up? I dunno, I'm just tired of the guessing games and want to get some more thoughts on this. I really appreciate the help as I'm extremely dissappointed and have no real solid advice yet.
 

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Wow, looks like you will have helio-coil the sparkplug for #4.. You didn't notice a miss or anything before this happened?
 

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Discussion Starter · #3 ·
Wow, looks like you will have helio-coil the sparkplug for #4.. You didn't notice a miss or anything before this happened?
what's helio coil? how is it different than re-tapping the thread?

I don't check the spark plugs often but I never noticed a missfire until that day when it all happened. I'm prolly not the best at identifying missfires but my first indication was the popping of the exhaust in neutral and no, that never happened until that day.

More pictures, had it towed, dolly style for a grand total of $82 and awaiting inspection monday, most likely.

I really hope I don't have to replace the whole ****ing head.







 

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When theres about 30,000 volts going through the plug, it needs to jump a gap. If it goes right through the plug like nothing, it will melt just like what happened there or the ceramic part will explode like a shrapnel geranade. lol
 

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Discussion Starter · #7 ·
What's this gap you guys are talking about?

I'm not sure on helio-coiling it because Jeff (Smaay) says "helicoils work for holes that bottom out, i dont think its a good idea to helicoil a hole for something like a sparkplug that is a pass though hole."
 

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When theres about 30,000 volts going through the plug, it needs to jump a gap. If it goes right through the plug like nothing, it will melt just like what happened there or the ceramic part will explode like a shrapnel geranade. lol
x2
sounds like the plug got smashed shut then every thing just got ubber hot.
 

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What's this gap you guys are talking about?

I'm not sure on helio-coiling it because Jeff (Smaay) says "helicoils work for holes that bottom out, i dont think its a good idea to helicoil a hole for something like a sparkplug that is a pass though hole."
Yeah I was thinking it shouldn't be either..that's why I said try the rethreader first. If no other choice I guess heli-coil....beats buying a head.
 

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I had a spark plug blow out in one of my old cars. I used a timesert to save the head. When that happened the spark plug was still tethered to the high tension lead. In your case, I guess the coil pack got in the way.
http://www.timesert.com/html/sparkplug.html

I was able to do it in the car with the head attached to the engine. The only problem was sometimes the insert would come out with the plug when removing the plug. Otherwise it worked fine.


ΔB
 

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Discussion Starter · #12 ·
^^^^ I'm pretty sure this is what the shop did today except the timesert has a few strands of jagged thread at the top for a more secure fit. He said he used some sort of Loctite to secure it to old thread. I'll try and get some pictures up of the timesert they used. Happy to have the car back on the road again with my new spark plugs and Matrix coil. It starts up a little different, a little more hesitation or something. I dunno, hopefully just the cold weather.
 

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I know this is an old thread, but how did the gap close? Is that actually possible? Did the piston do it? or the valves? or the pressure from high combustion? I really dont get this....
 

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Discussion Starter · #14 ·
It's all a mystery man. I really have no idea how this happened. It's pretty devastating as I think it's had permanent effects both on how the car runs and my enthusiasm for modding.
 

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I know this is an old thread, but how did the gap close? Is that actually possible? Did the piston do it? or the valves? or the pressure from high combustion? I really dont get this....
It can be a combination of things:

1. A flaw in the sparkplug production that led to electrode failure.

2. Some severe cases of knock have been known to cause electrode deformation.

3. Mechanical damage to the electrode.
 

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Aluminum head....Good luck. If the rethread works it will be very nice but hours of misfiring-abuse I have a feeling it probably f'ed up the thread pretty badly :( As for the coil to get damaged like that, the spark was probably arcing in the hole because of a crack on the coil boot. Good luck on the repair. Also, dont ever listed to idiots at Autozone for advice on car, they are morons!! Keep driving nothing will happen? Misfire like the one you had probably was flashing the CEL, which means you were roasting your Catalytic Convertor. I hope everything turns out well. Good luck with everything man.
 

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Discussion Starter · #17 ·
Well, this was repaired about 2 months ago. The mechanic first cleaned out remaining debris and gunk with a special super-succulent vacuum. I'm not sure if he even tried to rethread the head or maybe it just wasn't possible but he ended up putting this in. It looks similar to a timesert but with the top three threads being jagged. He said, for this, he had to precisely create new thread by hand (or do something very carefully by hand). Then he secured it with a special type of Loctite. I forget the PSI it can withstand but it was about 4 or 5 times that which passes through the hole:








Like I said earlier, it starts up a bit differently especially in the cold and it's a little noiser in idle. I now have 4 brand new Denso spark plugs and 2003 Matrix ignition coils in cylinders 2 and 4. Other than that it runs fine...


..about 500 miles later I got a CEL, there was no engine knocking but I pulled over immediately. I checked out the ignition coils and the spark plugs. Everything was fine so I reset the ECU and went home. Roughly 500 miles after that I got another CEL, no engine knocking so I went to Autozone to get it pulled. It was PO420 and I assume this was the code that I got 500 miles earlier. It's prolly been around 500 since that and it hasn't come up again but is it most likely one or both of the Co2 sensors or the cat itself?
 

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Discussion Starter · #18 ·
On the positive side, I'm certain my mpg has improved. Not sure what it was before but it's 32 mpg now. Most likely the new spark plugs.
 

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Just my thought, but is the plug in #4 the same size as the the other ones since the shop had to put that insert in? I dont think the size of the plug being smaller in diamiter would make a difference but if the gap is off you could have that hesitation of starting your experiencing.
 

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Discussion Starter · #20 ·
Just my thought, but is the plug in #4 the same size as the the other ones since the shop had to put that insert in? I dont think the size of the plug being smaller in diamiter would make a difference but if the gap is off you could have that hesitation of starting your experiencing.
All the spark plugs are the same size - they're all Denso Iridium SK16R11

But yeah it may be something with the gap. The plugs come pre-gapped (it's always a good idea to double-check though) but the mechanic was saying something like the plugs on cylinders 1-3 need 13 pounds of torque if you're putting them in with a torque wrench and the plug in cylinder 4 needs 13.5 pounds of torque.
 
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