SFI Chart C-4, Power Balance Test

This test checks performance of each cylinder by comparing it to other cylinders. PCM shuts off fuel for a given cylinder in its intake cycle. This measures performance of that cylinder by amount of RPM drop caused by that cylinder not producing a power stroke.

1. Idle quality should get worse when an injector is disabled. Engine should miss and idle will become rough.
2. Unequal performance of cylinders during this check indicates an ignition or mechanical problem, assuming fuel system has already been checked. Diagnose ignition system before checking for an engine mechanical problem.
3. If fuel system and power balance checks okay, check EGR, EVAP or PCV system for possible problem.

Fig 1: SFI Chart C-4 Schematic, Power Balance Test

Courtesy of GENERAL MOTORS CORP.

Fig 2: SFI Chart C-4 Diagnostic Flow Chart - 1 Of 2, Power Balance Test

Courtesy of GENERAL MOTORS CORP.

Fig 3: SFI Chart C-4 Diagnostic Flow Chart - 2 Of 2, Power Balance Test

Courtesy of GENERAL MOTORS CORP.