Cylinder Balance Test
A cylinder power balance test locates the cylinder causing a lack of power and not contributing to the engine's balance and performance. Use this and a cylinder compression and leakage test to pinpoint the problem.
The test measures each cylinder's drop in RPM, testing its effectiveness compared to the others. Each cylinder's ignition or fuel is disabled, and then the RPM drop is recorded at a particular speed (800-1000 RPM).
An engine analyzer or bidirectional scan tool does the same as this manual cylinder power balance test. It tests each cylinder and compares the results. When an analyzer is unavailable, the technician can disconnect the plug boot from its corresponding spark plug or distributor connection long enough to disable the desired cylinder.
Notice the drop in in rpm as the cylinder is disabled. If a cylinder's drop is inconsistent with the others, this indicates a problem with that cylinder.
A cylinder may not contribute because of an ignition problem, fuel delivery, or a mechanical problem such as a faulty valve or worn piston rings. There may be more than one cylinder involved. A faulty head gasket, a cracked head, or block results in a problem with adjacent cylinders.