Chevrolet Repair: 1990 chevy van idle problem, mass air flow sensor, air flow sensor

Question
Hi Tom,my 1990 G20 van with a 5.7L TBI is idling/'loping' and stalling. runs good and throttles fine at higher RPM.haven't noticed any exhaust smoke.disconnected EGR,idle became too high.check engine light came on when i drove it home but it didn't stay on constantly.sprayed for vacuum leaks,noticed no changes.new fuel pump around a year ago.replaced one injector connector.also noticed when i remove an inj connector,it runs almost "normal".and when I put it back, it's back running bad.do the different color wires on the inj connectors make a difference?can a injector "dump too much fuel? I"m going crazy,please help me!! lol   Thanks!!!!!

Answer
HI TRENT,,YES A INJECTOR CAN DUMP TO MUCH FUEL BEING COMMANDED TO DO SO BY THE PCM,OR IT IS STUCK OPEN ,BUT IF IT WERE IT WOULD KEEP SPRAYING FUEL AFTER YOU TURN THE ENG OFF,THIS WOULD DEPLETE THE PRESSURE IN THE SYSTEM,CAUSING LONG CRANK TIMES TO START. THE COLOR OF WIRES WILL NOT MATTER AT THE HARNESS BECAUSE THE PLUG IS NOT INTERCHANEGABLE. WHEN YOU REMOVED THE EGR VALVE THIS SHOULD NOT MAKE THE IDLE HIGHE, UNLESS THE VACUUM HOSE IS HOOKED TO DIRECT VACUUM,WICH WOULD CAUSE A LEAK, RAISNG THE IDLE..THIS VACUUM SHOULD BE ON A TIMED PORT..TURNS ON OFF IDLE NOT AT IDLE... THERE SHOULD BE NO CHANGE AT ALL ?? ARE YOU ABLE TO SCAN THIS ENG WITH A SCAN TOOL??? THIS MAYBE CAUSED BY A SHORTED OUT OXYGEN SENSOR..OTHER CAUSES,, BAD MAP OR MASS AIR FLOW SENSOR,[WHICH EVER ONE THIS ENG HAS]YOU COULD TRY TO REMOVE THE WIRE HARNESS TO THE MAP OR MAS AIR FLOW SENSOR AND SEE IF THIS HELPS THE PROBLEM. IF SO MORE THEN LIKELY THIS IS THE CAUSE..HOWEVER I WOULD GET THIS SCANNED AND RUN A LIVE DATA FLOW TO SEE WHAT THE VALUES ARE ON THIS ENG...LET ME KNOW HOW YOU MAKE OUT WITH THIS. I WILL BE WIATING..TOM..