97 Nissan Truck chugs and stumbles thru acceleration

[luckyfourwire]

What I know:

My 97 Nissan 4x4 chugs and stumbles during acceleration.

Usually during acceleration through the first three gears and usually after its been rainy or humid.

The engine will rev and the rpm will slowly increase but the speed sticks until something gives and then the truck accelerates quickly until I try to move into the next gear and the process happens again.

The chugging usually only occurs during the first 10-15minutes of driving after the truck has sat overnight or for an extended amount of time. Often it will happen in the morning, fix itself on the 20min drive to work, the truck will sit while I'm at work all day, and then start fine in the evening.

Only recently have I actually had a problem getting the engine to start after rainy/humid nights. The engine will turn over but not catch unless I leave the starter turning it for an extended period. And even after it starts I have to keep giving it gas to keep it running.

I've read other posts that suggest changing the distributor, contacts, plugs, and wires. But I've also read that since the engine rpm revs fine in neutral that the distributor, contacts, plugs, and wires aren't the problem...Maybe the time belt/chain...

I'm not skilled enough to do the work and don't have a trusted mechanic yet where I just moved and would like to be able to give some kind of direction when I take the truck to the shop down the street.

Any ideas? Much appreciated.