Problem when idling

1992 Chevy S10. when the engine turns over, the rpms skyrocket, immediately followed by them dropping so low it sometimes stalls out. I have to give it gas everytime to keep the engine from stalling. even letting off the gas to go from park to drive, it sometimes will stall out. whats the problem?

Could be any of many problems.

Any check engine lights or codes?

Have you checked and or cleaned IAC valve or egr valve And TBI buttery fly?