I need help from the forum please.

I was driving on the freeway and suddenly my engine RPM dropped really low got all indications and I figured it had to be the ignition system. Checked my #3 coil pack and it was 1/3 broken. I’m like F..K..I clean above the area where my spark plug is installed as much as possible. Then tried to unscrew the spark plug. It came out rough at first, but finally it loosens. As I examined it, it was damaged and damaged in the threads. i believe some little pieces fell inside too. I tried to create a suction on top of the coil pack insertion point and vacuum it out, so I’m unsure if everything is out or not. My main observed issue is the female threads for the spark plug. I need to be chase the threads or clean them out.

1.) What size tap do I use?
2.) With small pieces of spark plug broken off, I am unsure if pieces are in the combustion chamber. Also I will have to tap the threads. Will it be okay to start my engine and just allow it to blow out the exhaust port?

The spark plugs I bought were Bosch brand and Duralast Coil packs.

Thanks for reading, and thank you if anyone can help.



#3 Coil Pack



#3 Spark Plug


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You're best bet is going to be to pull the head and check for any damage to the piston and chamber first. The damage to the plug does not bode well for this.

 

That looks a lot like the spark plug came loose and of course with the ignitor on top holding it in it just melted, from the flame or the spark or both.
Check the tightness of the other plugs, pull any loose ones for a check.
As a matter of practice I always ignore the torque suggestion on new spark plugs and tighten till the washer is crushed flat. Never had a plug back out after doing that.

As you were on the freeway driving, I think a lot of any debris will have passed thru the engine already, so there would just be the debris that dropped in during removal. You may be able to put some large PVC tubing thru the spark plug hole and adapt it to your vacuum cleaner, move it around and suck out any debris. Then check with a borescope - or pull the head off.

You should be able to measure the OD of a spark plug thread and then measure the pitch and get a thread chaser for that. Pack the chaser with grease to catch debris. This will actually best be done from the inside out as no doubt the outer threads will be damaged - so you may have to pull the head anyway.
If the threads a really bad, it may be possible to helicoil them. Probably something that should be done by a shop.

With the head off (or with a borescope,) you should check the cylinder walls for damage. Any deep vertical scratches will allow oil to be sucked by the piston rings and compressed air and fuel to go the other way.

Good luck and keep us up to date with how it goes.

 

What Bosch plugs were those? Looking at the plug and what the threads look like, given that the plug is metal, I'm guessing the head took the brunt of the heat being that it's aluminum and you definitely need to look at the threads.

Like RichBinAz said, try to borescope it. Unfortunately, I don't think you're going to be able to simply 'clean up' the plug threads with a tap and you will likely have to Helicoil it.

Was there any indication of a loose plug as you were driving? It would have definitely made a noise and sounded similar to an exhaust leak when that plug started to loosen.

 

Not good! Hope the rest of the machine is ok