So i just bought the truck the 24th and when i bought it i knew that it wasnt 110% perfect, its an 87 pathfinder with 135 someodd thousand miles that seems pretty well maintained for $2500+tax. there are minor things wrong with it that would only cost a little time so no worries there, but one thing i am not too sure of what it could be is this: shifting from 1st to second and second to third i will give it a little more gas then it needs to go(i am still getting used to driving an AWD truck from a geo metro), but when i do that the truck starts to rumble and shake. When i ease up on it, it accelerates and drives perfectly. My guess is that it has something to do with the fuel system, the fuel pump mainly, i havent taken a real in depth look under the hood yet, so thats what im hoping it is and i can clean it or get a new one put on. Thats my only guess on what it could be though, any advice on any other things i should probably check out to make sure?

Thanks!
Mike, the new guy

The fuel pump is in the gas tank. Not a likely culprit however.
I suspect other things. Start by replacing the distributor cap, rotor and spark plugs.
Replace the fuel filter, which is mounted on the passenger, inner fender.
Check every single vacuum hose on the truck for cracks or leaks. Replace them as needed.

All of this is important on a used vehicle in order to get off to a somewhat fresh start.

When you get the running problems worked out, replace all fluids for good measure.

Thanks reserector, im taking a complete look at everything under the hood tomorrow to look for problems in anything else as well, everything helps!!!

rumble and shake when shifting:

could be indicator the flywheel needs to be resurfaced- for the clutch to get a smooth hold of it. Was the clutch recently replaced?

Welcome to the board. One other thing to check is if the timing belt was changed. They are rated for anywhere from I think 60K to 107K mile intervals. If the belt has slipped a tooth it would run poorly but if it is stretched it could alter the cam timing. Good luck.