My 1990 blazer stall almost every time I stop. I have replaced all sensors on intake and TBI, I also replaced all vaccume lines. New fuel pump,lines,and filter no codes found with scanner. Was told it could be speed sensor so i unplugged speedometer, now it stalls every time.Truck will idle all day in park,with or without speedo plugged in. OUT OF OPTIONS PLEASE HELP!!!

 

Have you checked the transmission electrical connections. The ECU should be able to tell the the transmission is in gear and adjust the fuel induction for the greater demand of being in gear. Same as when the A/C is engaged. If you have access to a scan tool you can check all the settings. This could be why you do not have an engine failure code because there are no parts failing. The ECU might not realize that the engine is in drive. The TBI itself is pretty straight forward. The other option is that the ECU is controlling the fuel signals properly but the injectors are not performing up to spec. There is no code for fuel flow through the injectors. My only other considerition is the Idle Air Control valve functioning correctly. If you can get a scan tool you should be able to monitor the counts on the IAC to see if there is a change when the vehical is in gear. A scan tool in monitor mode could lead to a proper diagnosis.