Engine knocks 3.2 isuzu rodeo 2000 ? help

You don't say how many miles or give a service history, but, that said I would check the timing belt and tensioner. When tensioner goes bad is often is reported as a loud knock or tick. Usually most evident at low RPMs. Another low cost try is to use a can of seafoam in the oil now, run it a few miles, then change it for a high detergent, low viscousity oil and drive it a while to see if the lifters clean up. engine tick is very common, generally due to lifters oil passages getting sludged up a little for 2nd gen 3.2l's