hi guys new user with a 97 4x4 4.6 XLT with 110K miles. 24" wheels and 315/35/24 coopers. Recently while driving through the desert and pulling a uhaul trailer I was sidelined with a #8 cylinder misfire. At the only shop in about 100 miles they told me that the spark plug broke in half and the bottom half dropped down into the cylinder. I watched them take the broken plug out. So I know they are not lying. Turning the engine over with no plug shot air out of the cylinder so there should not be a hole in the piston but after replacing the plug the engine still missed and the code still read #8 cylinder misfire. They say it probably is a head problem and won't know until they take the head off. They say it will be a $1000-2500 fix. Has this happened to anyone else? Would I be better off swaping in a new low milage engine for that price? Maybe a 5.4? Could this problem be caused by the combination of my crappy gears and the taller wheels? It seems like this is a common problem but what is the best solution? You guys seem like you really know you stuff so I appreciate your help on this one.

 

spark plugs breaking in half are rare i have never seen one. i have seen lots of blown plugs but never split plugs.

 

thanks anyway, Has anyone else heard of this or am I the only one lucky enough to experience it?

 

Unbelievable that it went in probably on the intake or power stroke and not blown out from compression or exhaust

With that many miles, definetly change the engine with a nice short block or guaranteed salvage yard.

 

is it easy to do a swap to a 5.4 or even the v-10 modular? Has anyone successfully done this swap?

 

So the sparkplug split in half from top to bottom? I can't see how it would have dropped down into the head otherwise. Were the threads for the sparkplug fine? Was their any damage to the coil?

From reading this it sounds just like a typical sparkplug ejection, but somehow the sparkplug broke into 2 pieces. I would take off the coil for that sparkplug and check the torque on the plug and make sure that you aren't dealing with the typical crappy ford head/sparkplug ejection problem.

I would agree with the others, with that many miles you would probably be better off getting a newer engine then paying to fix your old one unless it's a sparkplug ejection failure. If it's a sparkplug ejection failure just do a search on here for the TIMESERT Big bore kit and do the insert yourself for a lot less money.


Your tires/gears should have nothing to do with this problem. Your gas mileage is probably taking a hit, but not your engine.

 

Yeah the plug split in half from top to bottom. The threads were fine but half of the porcelin inside of the plug was gone when we pulled the plug. I did not notice any damage to the coil. Unfortunetly I dion't think it will be as easy as re-tapping the head. So is there any info on engine swaps out there? Maybe a ball park price for a 5.4 swap?

 

What is the compression on that cylinder? If the compression is fine, then you have some other problem external to the engine like the coil pack is bad or somesuch. I can't believe they are recommending tearing your engine apart without even doing a compression and/or leakdown test.

 

they put a compression tester on it and the gauge read .5 lbs but I don't think they were doing it right because when they turned the engine over with no plug in it air shot out of the hole.

 

This is a long shot, but still a possibility.

If only the porcelin went into the cylinder, then you may not have any real damage, as it would break before the piston would.

The three things I can think of are as follows:

(1) The porcelin is stuck between the valve and seat not letting the valve close. This would show no compression, but you should be able to hear some popping in the exhaust or intake if this is the case.

We used to hold dollar bills flat against the exhaust pipe, and if an exhaust valve was burnt the dollar would suck up inside the pipe, or flap back and forth on the opening like a playing card against bicycle spokes.

(2) The porcelin got between the valve and seat, and the piston hit the valve and bent it. (head needs to come off)

(3) The porcelin got between the valve and seat, holding the valve open for a short time. This caused extra lash in the valve train, which allowed a cam follower to pop off the lash adjuster. This is a fairly easy fix, with just the removal of the valve cover and replacing the follower.

With #3 you would show almost no compression, but have lots of air moving out of the spark plug hole when cranking the engine.

Also, try removing the plug again. There might have been some porcelin left over that closed the gap on a plug.

I pulled a head one time for a miss after a piece of the carburetor broke off and went inside the engine. The engine knocked for a couple minutes, then went to a dead miss. After all that work the only thing wrong was the piece of metal bent the plug shut, and then went out the exhaust. (I was 17 at the time, and learned a real lesson from that incident over 30 years ago)

Lesson learned:
You may end up going in, but make sure the easy stuff is ruled out first.

 

hey thanks for the info. I will definetly be armed with some knowledge when I talk with my mechanics!