#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?

 

[2000StreetRod]

Misfire criteria

The PCM detects a misfire when the power pulse from one cylinder firing appears to be weaker than normal. I would add a bottle of fuel injector cleaner in case the injector is clogging. I would also perform a compression test to see if #4 is lower than the other cylinders.

 

[Opera House]

The old number four! Had that problem with my 97. Are you loosing very small amounts of coolant? Believe it is the intake gasket leaking. My plug looked absolutely fine but replacing it with a $1.37 spark plug got me another 1500 miles. Sold it to a friend and he is still doing the same thing. Neither of us put many miles on it so at a couple of bucks a year wasn't worth doing the right thing. Hasn't gotten worse in years.

 

[robertoa1a]

Checking the spark should be kind of a no brainer. Take out the plug and see if it has dark coloration. If so clean it. Check the wires for resistance or swap two to see if the problem changes.

Rarely do we have problems with fuel injectors.

Carbon build up in the cylinder may be the cause. Does the engine sound like one cylinder is running against the rest (pinging)? If so run some high octane fuel and if the CEL stops then it's carbon. In that case use a can of Sea Foam. There are dozens of threads here on using Sea-Foam.