Engine running rough /spark plug gap

[Scottintexas]

My daughter’s 1989 grand wagoneer started running rough two weeks ago
I measured the exhaust manifold and [HASH=7780]#1seemed[/HASH] very cool
Pulled the plug and found no gap

Can gap just go away?

She worked at a dealership and about the time it started one of the boys helped her change the oil and didn’t know if he was pranking her

 

[Babin Farms]

I’ve pulled plugs that have done that with no reason also. Put a new one in and all was good. Hopefully this is the case for you.

 

[Cobra Jet Steering LLC]

all the plugs or just 1 plug?
it can be caused by a bad rod bearing to check it you remove the plugs and rotate the engine slowly by hand if possible until the piston for the questionable cylinder comes to the top, then rotate it just a bit until the piston starts to drop and go down, now stop and use a screw driver to push on the top of the piston , it should have NO play if it has any play or you feel a clunk when you push down on the piston it is telling you the rod bearing is going bad.

 

[Neutron]

Make sure they are the correct plugs. Seems the threads are long and grimy at the end half. Like its too long. If this is the case it would be the reason. The correct plug should be plenty far away from the piston. Valves usually get hit before a plug does if a piston travels too far or out of time.

 

[David Martin]

Lot of carbon built up on that plug.........maybe a piece of carbon broke off of the piston top and got smashed onto the plug causing the squish. Plain weird, just saying.

 

[AZMark]

Looks like something hit the ground recently on the upper right in your pic.

if it has been that way for a long time there’d probably be more buildup between the tip and ground.

 

[AZMark]

So I vote sabotage (or any of the above)

 

[zipper]

I hate to think that anyone would do that to a young lady. Pretty shitty thing to do! Did they mess around with the plugs during the oil change? Maybe one was dropped.