Howdy Ford ranger owners.
I have a 2000 Ranger XLT 4x4 with 4.0 engine Runs like a top until it some how stops firing in 4th cylinder after about 2,000 miles. Engine will start ideling very rough( Engine light will turn on) and miss badly when driving it. So to fix this I change the fourth spark and instantly the truck runs like a top for another 2 000 miles although some times it will ideal rough with out engine light turning on and I gun it a couple of times and then drives fine. Had one car mechanic say " Its either a vacuum leak,bad fuel injector,warped head,or Bad valve..... Truck has been doing this since 29,000 miles it has 62,000 now. I can easily pass other cars going up hills. Another mechanic says its the coil or maybe I could just change that plug wire?????? So what is my problem? Truck doesn't burn oil.When I remove spark plug it doesn't look burnt,some times it looks like the gap is bigger then the .054 its supposed to be. Also its a gas guzzler about 15 miles to the gallon I have off road tires on it.Oh its a automatic transmission.

 

my truck eats spark plugs every 8,000 miles,cant give you an answer.

 

This is a fairly common complaint on the 4.0L OHV like yours. The intake manifold to head gaskets may begin to leak slightly and #4 intake runner can suck a small amount of coolant from a nearby passage. The symptom is a misfire of plug #4. The fix is new gaskets.

 

I just started carrying extra plugs and the tools to change it... lucky for us it's #4 and not 3 or 6... that would suck...

 

Oh dang sounds expensive. Truck has a bunch of power. However just today over heated to and from work. Hope the problem isn't related. I think it might be a thermostat.