Toyota Repair: 1988 corolla high miles 150,000 or so, piston pin, stethescope

Question
Hey there
I have bought a 1988 Corolla with 4af auto with od. It has a knock in the engine when running, it is a bit louder a start up and then quiets somewhat. Is there perhaps a common problem with this engine. I bought a stethescope and can really hear the noise around the fuel pump. I am somewhat experienced but can not locate the noise. I am hoping for an easy fix? What do you think?

Answer
Any kind of knocking noise in the engine is not good news, noise that is louder when the engine is cold and then goes away or gets quieter is normally related to a piston failure or a piston pin,  there are no common noise problems with this engine, I suspect there is a major problem with the engine, it's probably why the other owner decided to sell the car. My suggestion is to have a professional listen to the noise and diagnose it.