Hi All, I have a 1991 nissan hardbody 4 cyl. I was driving in my work area and the truck lost about 50% of the power. Still starts and runs but feels like someone unpluged 2 of the spark plug wires. I changed the plugs and wires still same thing. OIl looks fine and has been changed regularly. Truck has 118,000 mile. Does this sound terminal? Can anybody give me a pointer or something to try. Thanks