1999 ford ranger 4x4 4.0 ghost in the machine

[foorrrdddd]

Hi guys, I have been coming here for years, but just didn't get around to posting. I have a 1999 ranger 4x4 with 4.0 and 80,000 miles. A few years ago the check engine light went on and a code reader said there was a problem with the #3 spark plug, wish I remember exactly what it said. It was about time to replace plugs and wires anyway so I did. A few months later the truck was running rough and a day later the check engine light came on with the same message on #3 spark plug. Obviously the #3 plug quit firing, which explains the truck running very rough on only 5 cylinders. So I replaced the coil pack, and put a new spark plug in #3. Truck runs fine for 3 or 4 months then starts running rough again with the same problem. All it ever takes to clear this up is replacing the #3 plug. Now, this will help some. I realize the manual calls for 2 different plugs in diff. cylinders. A ford tech. put in the right plug when the truck was in for a recall on something else and it wrecked that plug too. Taking the #3 plug out, after it starts running rough and the light comes on, it looks tan just like it should and there is no pitting, oil, or any corrosion of any kind, so I think I can rule out oil or antifreeze from wrecking the plug. Does anyone have any ideas on why only the #3 plug needs to be replaced every 3 or 4 months. Thanks

 

[delexploder]

Is it a sohc or ohv 4.0 ?

 

[foorrrdddd]

thanks for the interest. Does not say on original window sticker, and called dealer and they were absolutely no help in determining sohc or ohv. Also they were no help in figuring out why the plugs in 1,2, and 3 are different than 4,5, and 6 as stated in the owners manual. Original sticker only says 4.o liter EFI feedback fuel system.

 

[1Aauto]

welcome to the site

 

[foorrrdddd]

thanks