Cylinder 4 misfire. Vehicle exhibits misfire after normal operating temperature is reached and vehicle is driving a short distance. Spark plug, spark plug wire, ignition coil and fuel injector have been exchanged all check good. Injector signal has been verified and is good. Ignition coil wiring including: power, ground, reference ground, signal have been verified and are good. Stethoscope placed around #4 cylinder shows a faint knock in that cylinder which is not heard on any other cylinders. What is the probability of the AFM lifters in cylinder 4 unlocking prematurely after the vehicle reaches operating temperature ? Is there a way to check the VLOM solenoid for that cylinder or are they all activated at the same time ? Please Help with this issue. I do not have a scanner capable of actuating the solenoids or performing any of the associated testing of the DOD system.

Cars & Trucks - GMC - Envoy - 2007 GMC Envoy Denali