Chevrolet Repair: 89 Chevy Caprice, obd2 scanner, chevy caprice

Question
I have an 89 chevy caprice that cranks and idles fine. However, when I put it in drive, I have to keep engine running high or it chokes down.

Answer
HI TIM, THIS IS A TOUGH QUESTION BECAUSE THERE ARE MANY THINGS THAT CAN CAUSE THIS. I WILL ASSUME THAT THIS IS A V8 ??? TBI INJECTION ??? I WOULD CK THE IAC[IDLE AIR CONTROL MOTOR] IT MAYBE DIRTY  AND HANGING UP NOT ALLOWING IT TO IDLE. IT MAYBE JUST A FAULTY IAC MOTOR. OR CK TO SEE IF THERE IS A BUILD UP OF CARBON ON THE BACK SIDE OR BOTTOM SIDE OF THE THROTTLE PLATE. IF SO CLEAN IT OFF WITH A FUEL INJ CLEANER OR CARBURETOR CLEANER. SEE IF THIS HELPS. IF THIS DOES NOT HELP YOU MAY HAVE TO GET THIS ENG SCANNED WITH A PRE OBD2 SCANNER. THIS WILL HELP CK DATA FLOW AND MAY FIND THE PROBLEM IN THIS AREA OF DATA..THE LAST THING I CAN THINK OF IS A EGR VALVE THAT IS NOT CLOSING ALL THE WAY AT IDLE. THIS WILL CAUSE A STALL OR ROUGH LOW IDLE. LAST BUT NOT LEAST. MAKE SURE THERE ARE NO BROKEN VACUUM LINES TO ANY SWITCHING VALVES OR SOMETHING OF THIS NATURE.. GET BACK TO ME WITH MORE INFO IF YOU CAN... TOM..