1996 Land Cruiser Misfires Options

[Derrick]

Hello all, I am 15 and am know a moderate level about engines. I love landcruisers and my dad owns 2. His older one (1996) misfires under load. We will be accelerating and it sputters and feels and sounds like it is missing one more then 1 cylinder. It is very jerky and feels almost as if it is only hitting on 4 of the 6. The engine is the 4.5 l6 and this thing has about 208,000 miles. So far I have replaced the distributor and the plugs and wires that didn't help. Any ideas of what is wrong? I was maybe thinking the cam sensor or cam shaft but it only misfires under load. If in park you can put the pedal to the flood and it revs fine. A recent happening with the truck was the fan belt broke. We were driving down the interstate and the fan belt broke. The engine was running super hot and we drove it for about 10 miles to out house when my dad parked it and got the other one. It needed a new radiator and a shop put that in, it was misfiring before that and still does after about the same.

My dad is going to take it to a shop soon, he doesn't know a lot about engines but thinks it may be the fuel injectors. I was thinking that may be but it only does it some of the time and at times it is worse then others. I was also thinking it may be something with the transfer case which we have had replaced once cause it failed, like maybe it is popping out of gear or something. The only thing that disproves that is that the engine gets slower when it is misfiring not faster and if it was popping out of gear it would rev higher, right?

Any help is greatly appreciated,

Thanks!

Derrick