Bought a new engine from 505 because old engine was knocking. Replace with 3.9 performance engine from 505. Installed engine only ran on 3 cylinders. Have replaced every bolt on part including crank sensor, cam sensor, throttle body, coil, plugs, wires, ecm, o2 sensors. I am sure I am forgetting something. Engine starts runs rough. Cleans up slightly with higher RPM will not idle. Confirmed spark compression to fuel. Fuel via noide light and wet plugs. Spark with spark tester. Compression via gauge. Confirmed timing. Replaced injector on one of dead cylinders. Have removed and tore down motor and inspected multiple always same 3 cylinders that are not firing. Please help.

 

Welcome to JKF.. Interesting issue, What did 505 advise, being as it was purchased from them? Any warranty?

 

They have given a few things to try. We are working with them to resolve it.