Bad plug in Cyl# 4 twice in 10 months - what's up?

[ajr2000]

I just got done replacing the plug in the #4 Cylinder in my mom's 2000 OHV for a P0304 code.

10 months ago the same thing happened, same code, plug was replaced and it was off and running again. Had it fixed by the a shop tho.

What could be causing this to happen so often?

 

[aldive]

Can you post a picture of the spark plug in question?

Thanks ....

 

[410Fortune]

I would be prepared to replace the intake manifold gaskets on this engine AFTER looking at the plug and compared to others.

How many miles?
Does it use any coolant?

 

[NHale623]

What's probably happening is that you're treating the symptoms, not the problem. Changing the spark plug may have cleared the code initially, but did nothing to fix the cause of the misfire.

You need to determine and fix the cause of the misfire.

 

[ajr2000]

Al; I'll try to find the plug and post a pic tonight. It did break in half while removing it, not sure if I caused that. It was almost impossible to get out(See "Stuck Plug" in Explorer 911). I did look at it, and the plug seemed pretty clean.

410: It has 69k miles. It does use coolant, but it does have a slight leak.

NHale: The truck runs fine after changing the plug, so I'm not sure what you're saying.

Thanks guys.

 

[ajr2000]

Well, I couldn't find the plug to take a pic of it.

But the plug was just brown on the inside. Not too corroded. It is weird the plug broke while taking it out tho. Never had that happen before.

 

[Joe93]

could have dropped the plug and cracked it. That will cause a missfire and for it to break upon coming out. Try using a little dap of anti-sieze when putting in new plugs. Once you drop a plug toss it in the trash, it will only cause problems latter on.

 

[ajr2000]

Shop fixed this prob the first time (10 months ago) Pretty sure they didn't use anti-seize either.

 

[NHale623]

NHale: The truck runs fine after changing the plug, so I'm not sure what you're saying.

What I am suggesting is that the while the fouled plug is causing the misfire, I'm not sure you know what is causing the plug to foul.

The second time it was removed it was broken, but it isn't clear if it has been broken for 10 months or damaged when it was removed.

How does the color is the plug compare to the other spark plugs in the engine? Have you checked the plug wires?

 

[ajr2000]

Haven't gotten to the other plugs yet, plan to do that this weekend. I tried an old method for testing wires which I learned from working on lawnmower engines. Let's just say, the wire is good, and that coil pack has pretty good power to it.

 

[NHale623]

Something else to try is to start the truck at night. Pop the hood and disconnect the light bulb and look for arcing. It shows up real well at night.

 

[aldive]

Have you checked the resistance of the spark plug wire in question?

 

[Joe93]

Something else to try is to start the truck at night. Pop the hood and disconnect the light bulb and look for arcing. It shows up real well at night.

also helps if you use a spray bottle with some water. it will really get things jumping.