so i had a rebuild done about a year ago. they actually installed a different 4l60e instead of rebuilding the old one which was pretty much beyond rebuild they said. anyway, since i got it back when i put the vehicle in drive, almost immediately, it sounds like the truck wants to just shutter and die but goes on and off like that till about 25-30mph. they said its an engine problem so i took it to them and they replaced mass airflow sensor, worked for a day then back to same experience in drive. The only way i can shift is manually. note I also replaced shift solenoids in valve body and still no worky. thanks in advance for help

 

Vehicle info?

 

sorry 2000 blazer 4.3. i am having an issue with black ground wire from fuel pump that keeps shorting out too. traced that to a splice pack behind fuel tank. any other suggestions?

 

Check engine light on? Any codes?

First thing that pops into my mind is a faulty TPS. The computer adjusts a lot based off it's reading, from fuel delivery and ignition to transmission shift points.