how does this happen?

[snomaker321]

what would cause a spark plug to melt? I still think im going to get rid of my truck, but id like to figure out what happened. There is no compression in cylinder 4 and the plug melted. Engine still starts right up and runs easily. It shakes pretty bad at idle but seems to smooth out at higher rpms. Mechanic said I probably burned a valve.

On another note, would it be a bad idea to keep driving it? Could i do any more damage? thanks

 

[rurouni20xx]

congratulations you have reached a cylinder head temperature in excess of 350 degrees. this usually warps or cracks a head, serious lean conditions do this ive seen it once with an intermittently firing fuel injector. fired just enuff fuel to make that cylinder run super lean, melted the plug tip, warped the head, blew the head gasket and chipped the piston from detonation. is this only on one cylinder? you could still drive it but b4warned you need to fix whatever caused it (i.e. injector misfire or air leak from hell etc) and your probably going to start using oil on that cylinder pretty soon. best to figure out what happened and either rebuild or replace the engine whichever suits your needs better and make sure that you found and repaired the problem b4 you fry another motor.

 

[BRUTUS_T_HOG]

the spark plug being too loose can cause this. over advanced timing. lean fuel mixture.

if you keep driving it, it will likely do more damage.

and by no compression you mean ZERO pressure? not even a flick of the needle? check the other cylinders to rule out a bad compression gauge, my gauge has a sticky schrader valve that causes it to read nothing.

if you have no compression whatsoever in that cylinder and seeing that the spark plug was melted you either have a hole in the piston or a badly burned valve

 

[JP02XLT]

if you have no compression whatsoever in that cylinder and seeing that the spark plug was melted you either have a hole in the piston or a badly burned valve

Or Both of the above mentioned problems

I would check your temp gauge sending unit, If it is temp related you obviously were not made aware by the gauge or light.

JP02XLT

 

[snomaker321]

i had a misfire an cylinder 2 and lean bank 1 code for a while. finally got a chance to mess around with it had 5 codes, misfire 1,2,4 lean bank 1 and something about an emissions valve. We couldnt find our compression gauge so we ended up taking it to a mechanic to diagnose the problem. He stopped testing we he hit cylinder 4 and found no compression and a melted plug. As far as I know it never overheated and i never had a lean code on that side of the engine. Mechanic said it was probably a burnt valve now and the best fix would be a new engine which would be more than the truck is worth. I plan on selling/parting it out but i still want to know what caused this.

The kicker is it still starts up and runs fine every time. well, not exactly fine because it still misfires but it starts and runs. i replaced the plug with an old one and it seemed to be running a little smoother?

 

[Big Jim M]

Most times this is caused by an air leak after the throttle body. This air added to the fuel stream causes an extreme LEAN condition. As you prolly know adding air to the fuel mixture makes for a much hotter fire. The fire gets so hot that it burns up the valves, then the tip of the spark plug and burns a hole in the top of the piston or at least melts and misforms the piston.
If caught in time before the piston is harmed, the removal of the head and installing and then lapping in a new valve to the head will repair the engine.
All that usually is needed to make this repair is a headgasket set, new valve, some diamond grit and a full day to do the job under your backyard tree.
From your description of it running pretty good I'd guess it was saveable.
Big JIm

 

[Capt Jay]

If it's toast............keep driving it. You can't wreck broken parts. Just have your cell phone handy so when it fails, you can get a ride. If you plan on rebuilding it then stop driving it. If not................beat it to hell and show it who's boss. Do everything you ever wanted to it. Hell, don't drive it to the mall, drive it through the mall.

 

[rurouni20xx]

to be honest it almost sounds like a leaking intake manifold gasket on the lower plenum. you can smoke a few cylinders and never overheat the entire engine per the gage as the gage reads coolant temperature, not head temperature. clogged egr wont hurt anything but lean cylinders or an entire bank is a problem since it can lead to this type of damage. if you wish to keep the truck id recommend finding the problem and make sure it isnt anything to do with an accessory system and install a new engine. or do like jay says and find the nearest mudhole/destruction derby and put a brick on the gas pedal. to be honest i wish i was closer to you id buy the rolling chassis off of you and swap in my 92 2.3 2wd setup or 93 3.0 engine, thats a pretty truck to hear this happen to.