1998 Ranger 4x4 4.0 V6 Automatic transmission. Hey guys just wondering how to go about this, im getting a misfire on cylinder 4, hesitation and jolting with acceleration on highway or up hills. I have replaced coil and wires aswell as plugs, i ordered an oem plug set from ford today as a last ditch effort because im thinking the ones i bought (non oem) may be the cause for the single cylinder misfiring. My O2 sensors read rich so i dont think its an injector problem. any thoughts?

 

Add a wallop of Techron Concentrate before a stint of local driving. You could be one of the lucky ones.

 

What does the #4 spark plug tip tell you about conditions in that cylinder?

Old spark plug if you still have it
But current spark plug may be helpful as well

Its helpful to compare adjacent cylinder spark plug tip to the misfiring cylinders spark plug tip so pull out both

To test if its a fuel issue unplug the 4 wire connector on coil pack for no spark
Crank engine over for 5 seconds or so(no start)
Pull out #4 and #5 spark plugs compare them
Light each tip with a match or lighter, flame should be equal

If #4 is dry then injector issue of course

Compression test
Cold engine, all 6 spark plugs removed
Test each cylinder and write it down
Compression test numbers are about the relationship between the numbers
If 5 are 150-160 but #4 is 120 then there is a valve issue usually, burnt exhaust valve