I recently took my 350 out of a 1991 chevy 1/2 ton 4wd and put the 350 from a 1992 3/4 ton 4wd in it. I put all sensors, EGR, throttle bodyP sensor, etc. on the 92 before I put it in. The engine starts and idles fine. As soon as I am under power, I get a check engine light and the code is knock sensor. I tried a new sensor, the original 92 sensor, the 91 sensor with no luck. Timing is TDC and when I tried the 92 ECM with the 92 knock sensor, the truck would not even start. At TDC with #1 up on compression, the rotor points to #7 cylinder, approximately. Wires are 1,8,4,3,6,5,7,2

Anybody have any ideas?

 

Does the truck run out good besides having the light on? There should not be a difference between a 1991 & 1992. When you set the timing are you unplugging the computer advance wire? It will either be under the dash just below the glove box or underneath the hood behind the black plastic panel that is mounted on the passenger side firewall. It has 3 plastic nuts holding it in place. This wire has to be unplugged when setting the timing and once it is set then plug the wire back in.

 

When the light is on, there is basically no power going up hills. On the flat, it is sluggish. I did not unplug the wire but will try that
Thanks, I'll let you know.

 

I bet that is it. If you don't unplug it the timing will be WAY off. Try it and let us know.

 

you were correct, thank you