rapid misfire/bucking at Hwy speeds

[camoit]

Have you changed the fuel filter. After 30 years they tend to get plugged and not flow enough at speed.
You will find that under the bed by the tank on the drivers side.
Also at that speed you need to look for emission side vacuum leeks since that is doing it;'s thing at speed also.

[geezer101]

Have you changed the fuel filter. After 30 years they tend to get plugged and not flow enough at speed.
You will find that under the bed by the tank on the drivers side.
Also at that speed you need to look for emission side vacuum leeks since that is doing it;'s thing at speed also.

...o.k. add that to the list. Forgot to add a tired ignition coil as well. They have a tendency to break down at higher rpm if the coil is 10-15 years old. It will cause power loss and poor fuel economy.

[yamahlr]

Drove me nuts for a while-you guessed it!Ignition coil. Find on flat highways and lower speeds thru the gears etc. Finally stopped by dealer, first thing top mech did was check of coil. Not totally bad but on it's way out. New coil- no more problems. Years later upgraded to Jacobs off road team system,haven'looked back since.