2011 Ranger 4.0 Missfire on cylinder 2

[suburban99]

2011 Ranger 230,000KM's 4.0 4x4.
Missfire on cylinder #2 only when cold.
New plugs, changed #2 injector, new coil pack, new wires.
Does it in the morning when cold. If I plug in the block heater at night it does not set a code in the morning. Truck runs excellent other than the misfire rough idle...smooths out after a minute or so. Thinking head gasket or intake gasket...
Have not done a compression test yet but will have to be when the engine is cold.
No oil in water or water in oil...any ideas?

 

[RonD]

I would start engine cold and shut it off right away, then pull #2 spark plug and have a look at it.
You could have a leaking valve guide on #2 intake valve, enough oil leaks down the stem when engine is off and is then sucked into #2 fouling the spark plug until cylinder/plug gets hot enough and oil burns off.

Same could happen with coolant and head gasket but you would probably have other symptoms.

 

[suburban99]

Thanks for the idea RonD.
I'll give it a try.

Unfortunetly it's the passenger side and the engine has to be removed to get the head off.
Anyone have a link to an online manual? Thanks

 

[RonD]

Not a manual but this thread has lots of good pictures for the 4.0l SOHC: http://www.explorerforum.com/forums/showthread.php?t=316471

For short term fix, you could try a spark plug one heat range hotter, and/or add .003 to gap, larger gap helps in cold starts and low RPM range.
Spark plug gaps are chosen for average driving and are not "written in stone", racers narrow the gap for better performance in the high RPM range.

And while it may have nothing to do with it, it could, only use Motorcraft or if not available use Autolite spark plugs, the 4.0l's eat other brands, misfires at idle are one of the symptoms.
A nickle or copper Motorcraft is better to use than any other brands Platinum plug, Autolite is an exception since they make the Motorcraft spark plugs, but to a different standard, so not exactly the same.

 

[suburban99]

Thanks for the links Rond
This is my son's truck and I listened to it this morning when it was miss firing.
Has a noticeable valve tick on the passenger side.
I guess it could be a valve guide cracked...

 

[suburban99]

Missfire fixed...

Removed engine and head, #2 and #1 intake valves were completly worn... #3 was fine. Took it to have the head redone and the tech said he had not seen one like this...valve edges were paper thin. Ran fine when warm...