2000 Explorer with cracked porcelain on a spark plug.

[jzvosechz]

I have a 2000 explorer with a 4.0 ohv motor. the number 4 cylinder keeps coming up with a misfire code. When the plug is removed the porcelain inside the head is cracked and half of the porcelain is missing. Have changed the plugs and wires the first time and just the plug twice after. Have also removed all injectors and soaked them in carb cleaner over night. The injectors were then reinstalled with new o-rings. It takes about 100 miles before I notice a rough running condition and the check engine light comes on again. The code only comes up for cylinder four. All plugs look to be firing ok, even number four on the half of porcelain left (no carbon build-up,no discoloration-not orange like lean not green like coolant leak) have asked many people no one is sure about path to follow to resolve

 

[BrooklynBay]

Welcome to this forum! I've moved your thread into the stock 95-01 section. Do you know what the code number is?

 

[Rick]

Possibly a lean condition in that cylinder causing detonation which breaks the ceramic. that's all I can think of...

 

[coonerboy]

Did the broken porcelain piece fall into the cylinder? If it did that could be a big problem.

Are you saying you are on your 3rd plug for the #4 cyl? It keeps breaking after you put it in?

 

[corkey]

hmmm they are resistor plugs, so it will not fire properly with 1/2 the porcelain missing, replace the plug,,

 

[coonerboy]

hmmm they are resistor plugs, so it will not fire properly with 1/2 the porcelain missing, replace the plug,,

Right on corkey! The high energy spark WILL seek the path of least resistance. I have seen spark go through hairline cracks in spark plugs. Change the plug. If it keeps cracking after you put it in, figure out why it keeps doing that. Good luck.

 

[GCDMD]

hmmm they are resistor plugs, so it will not fire properly with 1/2 the porcelain missing, replace the plug,,

The man's dead on. I actually went through this problem on my 97 SUHC...I mean SOHC. There was a hairline fracture that wasn't visible unless a bright light was near it. That small fracture was enough to cause a P0171 code and a severe miss at idle and load. I would recommend replacing all of the plugs at the same time. Another thing to add: make sure there are no "gaps" in the porcelain. Gaps indicate the porcelain fractured and separated- possibly in your block. That is when it gets scary.
Forgot to mention that I have received a cracked spark plug from the store. Carefully inspect every plug before inserting into your engine, regardless if it is new or old!!!

 

[Rick]

hmmm they are resistor plugs, so it will not fire properly with 1/2 the porcelain missing, replace the plug,,

Have changed the plugs and wires the first time and just the plug twice after

He needs to find out why the plug keeps breaking each time he installs a new one... I stick by the lean condition causing detonation in that specific cylinder...