Hi. My 1992 XLT Ranger (almost an Explorer) has the check engine light on most of the time for over a year. Occasionally the light is off after I start up, but nearly always comes on and usually stays on, for over a year. Still, the engine ran fine, most of the time. Saturday I changed one coil after I would drive and the engine would cut out, then go again. Old coil had a hole in the insulation on the bottom. So I have one new and one old coil. Auto parts store guy read the code and said it was a coil problem, one new coil now, same light. Didn't read the code again yet. Engine ran fine yesterday after the new coil. It has been hard to start for awhile, occasionally, some days worse than others and many days no problem starting. Today engine ran rough, no power, backfired through the exhaust and blew out the muffler. I thought someone was shot when I heard it, very loud. It will do 55 but it takes a long time, even in first gear it accelerates quite slowly. And it's loud due to the 'sploded muffler. Because I haven't done it in a long time, I changed the 4 easy spark plugs tonight and 3 plug wires, one of which was bad, the wire plug side came out of the boot, fell apart. So I don't hear the spark ticking, but it doesn't run better. It almost feels like the spark is super retarded, but I hear engine pinging sometimes. 3 plugs looked good, gray with some buildup and wear. Rear plug was darker. Haven't touched the other side yet. I do have to add oil every month or so, I see smoke in the exhaust when idling. I took off the snorkel from the air cleaner to the intake on the top of the engine to get at the wires, and ran the engine that way. Same problem. Ideas? This very low power problem happened once before, and corrected itself in a couple days. I'm not thinking I will be so lucky this time, 172,000 miles. Timing belt at 80,000. Engine will run with front coil disconnected, but not the rear one. Front one is new. Local tune up mechanic says spark fires in intake and exhaust. I wouldn't think it would fire on intake stroke, compression yes, BTDC but why exhaust? What should I try? Same guy wants $75 to diagnose and $750 to change timing belt, plugs and wires.