K10 Misfiring

[Fleetwood]

I have an 87 k10 that has started misfiring recently. When I first turn it on and I am driving it around it runs fine. Once it warms up it starts to misfire at throttle under load. When it's in neutral it doesn't do it. It is especially bad when I am going up hills and it gets worse as the truck gets warmer. It sounds like it is hitting a rev limiter. What could be the problem?

 

[Bextreme04]

When was the last time you did a tuneup? Worn cap/rotor/wires and worn or dirty plugs could all cause that. Make sure plug wires aren't shorting out on the manifolds too.

 

[MrHorsepowerLSx]

When you mentioned " sounds like a rev limiter" are you saying the transmission is slipping or that the misfire is so bad that it is not firing and the motor is pinging? Are you still on the factory TBI or converted to a carb?