#4 cylinder misfire

[iamdolfan1]

My 1999 (4.0) explorer started missing and the check engine light came on . Hooked it up and code read #4 cylinder misfire. Changed plugs (autolite) ran great. Same thing happened again about 1300 miles later this time i replaced the coil (accel), sparkplug wires(taylor), and plugs(accel). Ran great again. Then about 1500 miles later same thing again.I pulled the #4 cylinder plug and it looks fine and i replace it with a new one it runs great again. Any idea what can be causing the #4 cylinder to miss fire?

 

[Ray-Ray]

I have a 1999 4.0 ohv. What I have found was the porcelain around the electrode had a very fine crack......for some reason this has only happened with iridium plugs. Good Luck

 

[ranger7ltr]

Does the engine feel like it is down on power and actually missing?

In a lot of cases, the fuel pressure and/or volume is not sufficient to sustain the needs of the engine especially under load...You might not even notice it dropping off power-wise when the pressure drops due to a clogged/dirty fuel filter or dying fuel pump...

I ran into this very issue when my fuel tank was extremely dirty and rusty...Even with a new fuel pump and having a radiator shop clean out the tank, the rust came back and would mix with the sloshing fuel and the result was a coffee-colored fuel supply into the fuel filter which would eventually clog the filter and cause starvation...

Your fuel systems pressure should be 65+/- 8 psi and it should not vary throughout the rpm range...If the pressure drops as the load/rpm increases, the fuel pump is losing its ability to supply enough fuel under that loading...

 

[bluestream1]

Did you check the plug wires?

 

[rookieshooter]

I don't understand how the plug looks good if it is in fact misfiring. Seems it would be sooty, oily or drenched in gas.

 

[bluestream1]

I don't understand how the plug looks good if it is in fact misfiring. Seems it would be sooty, oily or drenched in gas.

If the injector is bad, and not working right, your plug may still look fine