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

Try replacing the igniter.

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
Truck will still start fine, just seems like its only on 2 or 3 cylinders. Will the ignitor still affect this. Thanks

My experience is that igniters and coils should be replaced every 120,000 miles or 10 years, whichever comes first. You qualify based on both parameters. If you don't replace them now, at least take them for free testing at Autozone or O'Reilly Auto Parts. I would also replace the distributor cap and rotor, if you have more than 60,000 miles on them. If you don't want to replace them, at least remove the distributor cap and clean to ensure there is no carbon tracking. It could be the secondary voltage circuit is directing the voltage back on the distributor, because it is having a hard time getting to the plugs. Make sure the inside of the cap and rotor are in good shape.

Check all of your vacuum lines to insure that they are connected properly.
Also, just as txgreasemonkey suggested, make sure that all the regular "tune-up" items are in good shape.
Hope this helps...