My 4runner runs fine, but when I am driving, and let up on the accelerator, a noise can be herd in the front of the motor, sounds loud enough to be a rod, but when I accelerate the noise is gone.....when I am driving and keep a steady speed, you can hear it knocking....any idea what this could be? Thanks

 

1) are you sure its the motor?
2) if it is the motor, could be a bad thrust bearing causing the crank to walk around and hit stuff causing the knock, or (and most likely) a timing chain guide broke.

Id see if you can verify that it is for sure the motor, if you havent already. If you are sure its the motor, pull the valve cover and look down at the chain and guides. make sure all the guides are still there. That would be a good start. If all thats good, post up and we can go from there!