I currently Finished swapping a 1997 Vortec 5.7 V8 into my 97 Vortec V6 K1500 pick up truck. I changed over the Wiring harness Computer sensors etc. The truck Fires up and Runs great but as Soon as I plug in all the O2 sensors the Truck starts to have a misfire. I tried resetting the ECU but the same issue occurs. Once I turn the truck off and unplug the 02 Senors it begins running normally. The senors were working fine on the 1996 Vortec and I never even had a check Engine light on. I looked up the sensors and there are the same number of sensors and types of sensors on the V8 Truck I pulled the Engine out of. Also the truck I removed the engine from had No misfire or anything and All sensors were attached. Any thoughts or Ideas on this Issue?

 

did you use the map sensor from the v8?, also check the connections into the computer for bent pins or something, this is wiered though

 

Make sure you have the plug going to the correct sensor. i.e. bank1 sensor1 to bank1 sensor 1
Does the truck run differently when the sensors are plugged in or does it just throw the code?