2003 Taco-- 62,000 miles

I was 40 miles outside of Raleigh, NC. Had been driving 11 hours from NY. All I could think about was my bed. Suddenly there was a loud chirping from the engine. It lasted about 20 seconds then stopped. Then it started again, followed by a bang, and then the engine shuddered. I pulled over.

Looking under the hood, the center spark plug on the passenger side had basically blown out. All that was left was the coil pack, with nothing below it. (Not even the rubber.) Because it seemed the cheapest option at the time I had it towed to the dealer in the town I was in.

Their explanation was that the plug was too loose. (Was this the clicking I had been hearing the past month or so?) The loose plug finally blew out, taking all the threads with it. If you tried to put a new plug in it the way it is, it would drop down into the combustion chamber. (Or whatever it is that's below the plugs.)

Does a loose plug seem the likely cause? What was that chirp right before the bang? (The bang being the plug hitting the underside of the hood.)

I haven't done anything yet. I've been making calls and such all weekend. Basically I've been given these options:

1. Replace the whole head with a new one. Obviously the most expensive.
2. Fit the head with a helacoil. Slap in a plug and a coil pack.
3. Put in a used head.

All of these would be done by the dealer where it is.

I have a fourth option, but this involves towing the car about 100 miles to a friend's shop. He's been a mechanic for 30 years. I trust him. (sort of...ha!)

He's willing to do it for next to nothing. I'd help him, which would be a good learning experience and all, but I'm not sure the tow would be worth it. We'd explore all options above.

Any thoughts?

(Sorry for the long post.)

Personally, take option 2. If you have someone with sergical hands and you work carefully, you can really grease up the tap and it will catch 95% of the metal shavings while you tape out the hole (i.e. leave the head on the motor). When you put the coil in you have to knock off the tang and that's going into the cylinder. Find out if it's magnetic, maybe you can fish it out with a magnet when you're done. Then get a shop vac and a small rubber hose and try to vac out anything else that fell into the cylinder. Not a perfect solution, but if money is an issue and you're really careful you might be able to get away with it.

PS-> Are you sure all the threads are gone? It seems unlikely that more than just the top couple of threads would be damaged; unless the guys at the shop tried to ram a new plug in before cleaning it up with a greasy tap.

A thought ... you may be able to fabricate something (a small cup) to place down in the spark plug hole (bring the piston to TDC), which would catch any shavings from the tap ... then once you've installed the heli-coil, you could remove the fabricated "catch" which should contain most (if not all) of the metal shavings. I say this because even if the heli-coil is magnetic, the metal shavings from tapping the head will not be (as the head is aluminum) ... and those metal shavings will not do any good for piston rings and valves.

I have heard of this happening before, you're not the first one.

Here is where I saw the problem before: http://www.yotatech.com/showthread.php?t=52838

Option two.

The tang is broken off and extracted via the pliers you use to snap it off, if you are like me, and I know I am.

The aluminum can be captured via a greasy tap. Most everything else will be 1) blown out of the exhaust valve within seconds, or 2) become one with the combustion chamber, and being softer than anything else in there, inflict very little if any detectable damage.

Turn the engine over until the exaust valve on that cyl is fully open(intake closed) then hook a good shop vac up to the tailpipe and tap away. We use this procedure on bikes all the time, just try to hold on to the tang of the helicoil. Or if you can find them, keenserts are a threaded sleeve with no tang to break off, they have drive pins alongside the threads to lock it in place <img src="/forums/images/graemlins/kewl.gif" alt="" />

It worked like a charm. I'm back on the road.

I'm very suspicious about this whole thing. The rest of the plugs weren't loose. I think that the one was either cracked or the coil pack was bad. I don't know. It seems odd. I wish I knew a Toyota mechanic who has access to information on how often this happens. Seems odd.

I'm glad I ended up towing it and doing it with a friend's help. Easy and $2,000 less than the dealership. Silly dealership.

<img src="/forums/images/graemlins/kewl.gif" alt="" />