Just happen I had the same problem two days ago. With a new to me, used engine I picked up from a PNP. The two inside plug were locked. With "absoulutely no movement" at all. The outside ones were almost as bad.

These were the tightest plugs I have ever run into in my life!

First of all you need lots of time and even more patience. The penetrants can only work down a thread or two at a time of course from the top. It needs help.

We are lucky that these plugs still use metal gaskets. Fill that depression around the plug with your favorite potion. I used all the brands I've tried over the years.

PB Blaster, Kroil, Maltby and my most recent and most expensive Corrosion "X". I forgot to use some ZEP because it was up at the house garage.

I suggest soaking, then time, tapping lightly with hammer, then time again. I expand this procedure.

I experimented very briefly with a propane torch about half way but concluded the the aluminium head was absorbing heat away faster than any expansion was going to occur. My engine is empty of coolant so with that you have a less chance of results. Plus you burn off the potion which could leave carbon residue. They are petroleum products!

Use your favorite socket and a 10" to maybe a 15" breaker bar at the most. This will make you use time as your friend! Be patient!

The method I use is apply enough force to "just" crack the plug by tightening or looseing. This stage of the game you are "grabing" at anything that might work! Then "Let" it sit some time soaking.

Then work your wrench back and forth just enough to hear it squench again. Let it sit so the potion can seep. Now here is my thought of "a secret technique".

You are dealing with having to work between two tight spots. One at each end of the stroke. When you stop to rest, to let the potion work. Stop half way in between them! This is when, there is the most clearance for the stuff to seep down. Tapping with hammer may be controversial but the theory for me is built upon this.

One,It lets me work at doing something. Lose frustration. It adds to the soaking time that is going to do the job. Time, did its dirty deed here. It got this plug stuck in the first place.

Second there are tiny flakes of corrosion trapped on the threads "V" side clearance. There is more clearance at the base or roots of each male and female thread. When they stopped sliding they try compacting themselves at the end of each stroke. Wedging is not good. If pressed further it leads to GALL. The thread ripper.

We need to use that space and allow them to drop in there!

Backing up. Slides, the now "compressed crudy self" back the to spaces where the potion can try to dissolve it. The hammer tapping "may" add some sonic power? The theory to possibly displace or shift their orientation.

Now with all these tools in our "hands". Space, potion, and motion... the 2 types if you will. We have another tool that will bring all of these in concert!

Rhythm! Yes, you read me right. The human factor.

You close one eye or eyes. Listen and feel. Working the wrench like a washing machine agitator except do a half stroke or quarter stroke thrown around or so. As as the human intuition kicks in.

You'll get tune in. The feel and sound will teach you what is far enough!

This is being mechanical while being a mechanic! It is also the difference between the thinking person and than some gorilla wrench puller.

Remember. Spock, had to close his eyes to become one. Same applies here! A little more push this way or that or just wiggle it. Also shaking some things, makes stuff come out better too. When I take a rest!

It's all about....Rest and motion for the potion.

So in time, it will lubricate/dissolve them little grimy rascals.

It took me 7 hours to patiently get four plugs out. I did walk away a lot and did other things. A little extreme for "time" but I have all good threads!

The primary objective was good threads. I work so cheap for myself, time doesn't matter.

My other, Plan "B". Was to take a deep welled hole saw cutter with a plastic sleeve insert and remove the crimp ring on the top of the spark plug base. Pick out the ceramic packing powder and then lift out the porcelain electrode. Then drill out the threaded center base of the spark plug like it was a broken stud or bolt.

Of course I haven't had to do that. I'd have to borrow the cutter saw and make my insert but it was a plan in this crazy man head.

Did I mention I was a R&D machinist once upon a time. I got paid to get creative back then. Now I'm just crazy at my expense!

Hope this helps any who chooses to apply it. Or if you are "stuck" with this problem, helps start a plan of action.

Phil

I've gotten used cars and faced this, too (and one of the reasons I do tuneups myself, so I know they're torqued properly).

Start up the engine and run it to normal temperature. The expansion of the warmed head will enlarge the size of the spark plug hole and possibly loosen the grip on the plug
[which may be contrary to popular notions that it will intrude into the hole and make it smaller :-) ]

Of course, this assumes that the reason for it being stuck is just being too tight (torqued too much), not cross-threaded!

Good luck.

The plugs have carbon on the first few 3 or 4 threads which can't be prevented,even with anti-seize.

As benski said, PB Blaster and tighten and loosening action with the wrench. I'll add, give it a shots of PBB over several days and try removing the plugs while the engine is hot.

I usually use an old plug with slots cut in the thread as a chaser and clean the plug holes with a solvent soaked towel wrapped around a dowel rod.

700/900FAQ: B230F/T and B234 4-Cylinder Engines: 18 +/-3 ft-lb or 25+/-5 Nm unlubricated torque per manual.

Reduce to 9+/- if you use anti-seize.

Tom

You might try slithering a little Kroil or PB Blaster down in the hole. And, incredibly enough, I have SOMETIMES had luck tightening the plug just a smidge before trying to loosen it. Anything that you can do to break that bond between the aluminum head and whatever coating is on the plug will help, obviously. You might even try warming up the engine and spray a little of that freeze spray that's used for finding cold solder joints in electronics boards onto the base of the plug. Otherwise, I see some heli-coil inserts in your future. Good luck!