Misfire on #4 cylinder

[Flaps]

I have a 2006 Ranger FX level 2. It has 130km (80k miles) and I'm starting to get frustrated at its lack of gas Mileage. (425-450km per full tank. 65 liters). Anyways I decided it'd be a good time to change the plugs. I bought a set of NGK plugs and gapped them to .061. I then put some fuel injector cleaner in gas tank. (I don't normally like using that stuff because I think it's hard on fuel pumps but I did)

So after a couple hundred KM I start to get this bogging or lack of acceleration at close to wide open throttle. One day it caused the check engine light to come on. The code it came up with said #4 misfire.

I took the plug out and haven't seen this before. I'm going to try the mass air sensor clean as I have read on here. Do you think I'll need to pull my injectors? Any idea what's causing this or why the plug looks like this?

I’m not sure if you can see it clearly but the plug has a copper / burnt look to the metal portion below the threads. Also a little bit of Burt color on the porcelain part. This is only on the one side of the plug. The rest of the plug is a little on the white side (possibly lean but hard to say since the plug is still fairly new)

 

[killj0y]

Doesn't look like anything is clearly wrong... Have you checked spark and fuel on that cylinder?

 

[Sasquatch_Ryda]

Remove NGK's and toss in garbage. Go get some Motorcraft AGSF24N plugs and gap them to the proper spec of 0.52-0.054"

And that is around 14L/100kms.....nothing at all wrong with that out of an SOHC 4.0L....

 

[monsterchuck]

+1 on Motorcraft plugs, but don't expect good fuel economy. 4.0 Rangers just do not get good fuel economy. Some do, but they are few and far between.

As for the misfire, could be a bad plug, injector, coil, compression, ect. Hard to say without looking at it. That plug looks like it has been firing. Are you sure you have the number four plug out? Number four cylinder is all the way to the front, left/driver side of the engine.

 

[adsm08]

So let me get this straight quick before we go any farther...

You take out your original plugs that still have 1/5 of their service life to go, replace them with something I wouldn't put in my weed whacker, over gap them, and then get frustrated when you start having issues right away.

Does that sound about right?