rec. fuel system clean. ethanol treatment to 1 tank of premium. ethanol blend in fuel causes build up fuel system , combustion chambers,exhaust, and causes increased wear to spark plugs. ford light trucks and SUV's from that year are known to have increased wear to spark plugs and coil boots on the left bank. i am guessing it has something to do with the exhaust set up. switched my personal vehicle to dual exhaust system to test the theory. so far so good.
I WOULD START WITH COMPRESSION CHECK LIKE ebans777 SAID BECAUSE THOSE YEARS ( 1998 - 2003 ) EXPLORERS HAVE A PROBLEM WITH LEFT ( DRIVER ) SIDE CYLINDER HEAD AND RINGS A SPECIALLY #5 CYLINDER ( MIDDLE CYL. ON DRIVER SIDE ) FORD MOTOR CORP. DOESN'T WANNA DO ANYTHING WITH IT
did it say multiple misfire if it did try the cam shaft sensor the same thing happen to me in my 2000 lincoln navigator the code reader said multiple misfire so shop said it may be that sensor so i would look into that its the cheapest 20 bucks for my suv