Knocks Cold and Continues For 2 to 3 Minutes

^ Engine flywheel contacting the splash shield. Reposition the splash shield.
^ Loose or broken crankshaft balancer or drive pulleys. Tighten or replace as necessary.
^ Excessive piston to bore clearance. Replace the piston.
^ Cold engine knock usually disappears when the specific cylinder secondary ignition circuit is grounded out. Cold engine piston knock which disappears in 1.5 minutes should be considered acceptable.
^ Bent connecting rod.