Spark Plugs Stuck Halfway Out

I would use a long extension/hollow pipe to your wrench (which will give you more torque), try to retighten the spark plug. I would not try and remove that.

Since this is a 2005, I would leave that spark plug in there until you one day get a misfire code. Then I would think about removing the spark plug. These iridium spark plugs (if that's what you put in there last time), lasts 150k miles or more. So if these are only 60,000 miles old, I would just retighten the plug back in.

 

I usually do a back-and-forth, back-and-forth action on those to avoid getting them to a really stuck condition. Since yours got stuck on the way out, it probably will be slightly easier to turn in the in direction from where it is now stuck. Observe I said "slightly easier" but did not say "easy".

If you can get it to go back in some, you can either put it all the way back in and fuhgeddaboutit as JC suggests, or you could go back to a frequent back-and-forth procedure and see if that gets it eventually the rest of the way out. Working in your favor, some of the penetrating oil you've put in there will be carried into the threads as you turn the thing back inward.

It can sometimes happen, though, that spark plug hole threads need to be Helicoiled after a bad episode of that. (And of course any chips and shavings then need to all be gotten out of the cylinder.)

 

Many of us would of just kept checking the threads are still there by screwing it in a little between each effort of increasing force to get it out. As long as the threads aren't crossed you can use a lot of force with a breaker bar without issue.

 

Yikes what a nightmare! Sorry that happened! Please don't spray anything else in there, whatever you use will end up inside the engine when the plug does comes out...not good for it.
I was taught, years ago, to always remove/replace plugs in an aluminum engine when the car is warm, not hot and not cold. I run them up to operating temp and let them sit for an hour or so until they are warm to the touch and always careful both removing and replacing to avoid the cross-threading nightmare.
Keep us updated!!

 

Might indeed be the cold Minnesota weather factor.

 

Stories like this make me glad that I just go to dealer once every six or eight years to have the plugs changed.

 

Out of curiosity, has anyone tried using graphite to lubricate the threads of sparkplugs? Normally applied as an alcohol/graphite mixture so it leaves a smooth even layer of graphite as the alcohol evaporates. I've used it on many things, but never thought about trying it on sparkplugs. Read somewhere that Champion used to offer tubes of this as lubricant for people who insisted on using anti-seize.

 

Smart! When in doubt get a pro to do it or, at minimum, a mentor who can teach you.

 

So what you are trying to accomplish is to re-seat the spark plug. If it won't come out, it shouldn't be that hard to reverse directions and tighten it back in. Your best solution would be to just tighten the plug back into place and drive your car. Don't change that out.

Here is an image of what you're trying to do with a pipe extension, slip a pipe over the socket wrench, to extend the length and give you a little extra torque to help you turn the spark plug. Just don't use 3 guys to do it.

 

No, I would not suggest trying to run the car (for very long) with the spark plug as it is. If you have the ignition coil (semi)installed, the plug would likely overheat because it doesn't have correct contact with the cylinder head- if it fired at all. If you removed the coil then you have a misfire - you could also unplug the injector so you don't melt the catalytic converter, but the hybrid ecu would throw codes due to low engine power ( and might possibly shut down the car?).

You likely have a condition where a bit of something mucked up threads at the bottom end of the plug. Trying to remove the plug has dragged this bit around and around- galling the aluminum of the head and smearing it into the threads of the plug. Now you have a "lump" of aluminum on the plug that's gouged and mangled the threads in the head.

Maybe you can idle the engine some to get things warm and try "back and forthing" to get the plug to do something. Maybe the plug comes out- along with most of the threads. Maybe the plug snaps off. Worst case the head has to come off. Maybe heat and some gentle use of an impact gun.

Last one I had that started to do that- well I tightened it again and it's still running fine over 10 years later (little old lady car with very few miles driven).

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Shortly after we bought our 2007 we had a trusted shop replace all the plugs, which they said was "very difficult". Had I tried it myself I might well have ended up in the same situation as the OP.

Running the engine with a plug in its current position seems like a bad idea. That cylinder isn't going to run right, might not even fire, and it could burn up the plug or cause it to blow out of the engine. If it were mine I would remove all the plastic and rubber bits around that cylinder and then try warming it up with a heat gun. Slowly. Then try to tighten it back up again with a torque wrench set so that you don't exceed a "safe" amount of torque. That wouldn't be much even if everything was brand new, 12 lb-ft for a 10mm plug or 18 lb-ft for a 12 mm one (I don't recall what size the Prius has). If the plug can be made to go in again without exceeding that "reasonable" torque on the last few turns then it may last a while.

Otherwise, there would be no shame in having a mechanic remove it and (almost certainly) put in a helicoil to hold the replacement plug. An experienced mechanic has probably been in this situation numerous times and knows how to proceed. Also, already has the tools to do so.

 

I don't think any of the responders were saying that; you would want to screw the spark plug completely back down and torque.

Second Gen Repair Manual excerpt, torque spec is 13 ft/lb:

 

The OP has "pulled a thread" while trying to remove the one plug. Don't know IF it's possible to go in or out without further damage to the cylinder head or breaking the plug off.

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