What could cause a 1998 Ford Explorer to start and idle but runs rough and dies in drive but not reverse?

He is some information on the O/D light...http://repairpal.com/overdrive-off-light- 648. You need to have the codes read. There are several thing that could cause the car to bog down.. throttle body may need to cleaned, crankcase sensor, clogged catalytic converter, fuel filter may be clogged and list can go on and on. Reading the codes is your best approach at this point.

Check everything Joe suggested. I would ask when is the last time you performed a tune-up (with Motorcraft parts)? You daughter's 99 has the same engine your's has. It's the old pushrod type engine which is a workhorse. She purchased it new. Her car experienced the same problem as yours. When I asked when was the last time she did a tune-up, she said "what's that" I suggest you check the resistance on the spark plug wires and primary and secondary resistance on the coil. You'll need a multi-meter. The "within spec" numbers can be obtained from the net. When I tuned up her vehicle it sounded like it was idling just fine. Checking it out while running I discovered it was missing on two cylinders out of six. Which caused the problem when the engine was under load.