ok so i bought this jeep for $500 and drove it about a 100 miles to my house. it ran perfect the whole way back. then a couple days later i notice a little knock coming from the bottom end. i also noticed the oil psi was a little low for what i like (10psi at idle, 20 to 25 psi the rest of the way up). so when the engine is cold there is no knock at all. once the engine warms up it starts to knock around 2000 rpms. so today i decided to put a high volume oil pump in and while i had the pan off i checked out the bottom end. the oil pan was clean which was a good sign. checked for any play in the rods and everything felt good. so i got it all back together and fired it up and had great preasure. but...... the knock is still there. the jeep runs great still but i want to find out what it is. the jeep is a 89 cherokee 4.0 manual. this is my first jeep so i dont know to much about them. from what i do know a knock is not good lol. any help would be great. THX

 

This is probably gonna be a question for the Renix familiar guys.

As we have Renix Jeeps (87-90) Its the software thats used. It was Pre-OBD.
I am new to Renix engines myself, PLUS this is my first 4x4 also, same as you, although mine does not have a knock.

Knock, knock...
Whose there?

YOUR ENGINE!

 

Bad fuel,

wrong weight oil

bad bearing clearances

Piston slap