Cylinder Power Balance Test
A cylinder power balance test compares each cylinder's effectiveness with the others. Ignition, fuel delivery, and mechanical problems such as a faulty valve or worn piston rings result in a weak cylinder. There may be one or more cylinders involved. For example, a faulty head gasket, cracked cylinder head, or block will cause an RPM drop on adjacent cylinders.
For many years, disabling a cylinder by removing the plug boot from its sparkplug was standard procedure. Check with the manufacturer's specifications; a prolonged open in the secondary ignition system may cause damage to the coil or ignition module. In addition, raw fuel flowing into the catalytic converter causes it to overheat. Sometimes a sensor, like an O2 sensor, will need to be disconnected so the computer will not compensate for the sudden change in conditions.
Notice the RPM drop as the cylinder is disabled. If it is not consistent with the others, this indicates a problem with that cylinder. An engine analyzer tests each cylinder and then compares the results. It is easy to do the same with pencil and paper. An engine analyzer or dedicated tool is best for testing coil on plug COP ignition systems. Check with the manufacturer; there are many ways to cancel a cylinder, such as disconnecting the fuel injector's connector.