96 j30 help!! po505 idle control system malfunction

[bill240sx]

ok i have a 96 j30 ive got codes for p0505 idle control system malfunction code. ive also got the knock sensor code. the car is also hard to start in the morning. i was told by identafix, a service the repair shop i work in to adjust the idle screw on the side of the intake manifold that controls the iac. i was told to warm the car up unplug the tps and then adjust. i did this and the light stayed off for a week. then one morning it was hard to start again and the light came back on. i adjusted it again and cleared the codes. the car starts normal in the morning again but the light is back on. i have the car for sale and i need to fix this cel light!!

[bill240sx]

any ideas??