Chevrolet Repair: 1990 Chevy Blazer 5.7L Throttle Body, fuel pressure gauge, mass air flow sensor

Question
Engine starts fine, 2-3 secs. later chugs and stalls. Sometimes I have to keep foot on gas to keep from stalling. Scanner shows no trouble codes. Just replaced 6 feet of gas vent line which was plugged and the fuel pump relay. Runs fine on the road. Lack of fuel pressure maybe? Or could this be a vaccum line problem? No engine service light warning. Also had throttle body cleaned and the gaskets replaced. Had the idler controller replaced 4 years ago.

Answer
HI WALTER,I DON'T THINK WE HAVE A FUEL PUMP PROBLEM IF IT RUNS OK ON THE OPEN ROAD. THIS SOUNDS TO ME LIKE A BAD MAP OR MASS AIR FLOW SENSOR OR IAC MOTOR.[IDLE AIR CONTROL MOTOR.]. TRY TO DISCONNECT THE MAP OR MASS AIR FLOW SENSOR [NOT SURE WHAT THIS ENGINE HAS] AND SEE IF IT IDLES BETTER,NOT PERECT BUT BETTER. IF SO, YOU FOUND YOUR PROBLEM. A PARTIALLY OPENED EGR VALVE WILL ALSO CAUSE THIS,TRY REMOVING THE VACUUM TO IT,SEE IF THIS HELPS.  IF YOU HAVE A FUEL PRESSURE GAUGE YOU COULD CK THE PRESSURE AT THE CK PORT BY TBI [THROTTLE BODY]SHOULD BE 32 TO 35 LBS. BUT I DO NOT FEEL THIS IS A PRESSURE OR VOLUME PROBLEM,AT HIGHER SPEEDS THIS PROBLEM WOULD WORSEN. A VACUUM LEAK WITH FUEL INJ WOULD MAKE IT IDLE HIGHER THEN NORMAL. YOU MAY ALSO HAVE A DIST PROBLEM,SUCH AS PICK UP COIL..CK THIS FOR YOUR HOME WORK AND GET BACK TO ME WITH MORE INFO. HOPE THIS HELPS YOU TOM. WHEN YOU LEAVE THIS SITE WOULD YOU PLEASE RATE THIS ANSWER.THANK TOM.