ADV4 - Check Vacuum Diaphragm

Vacuum Advance:

^ Disconnect and plug the vacuum hose(s) from the vacuum diaphragm.

^ Connect a Rotunda Vacuum Tester 021-00014 or equivalent to the vacuum diaphragm.

^ Connect a Rotunda Timing Analyzer 059-00014 or equivalent.

^ Engine at idle.

^ Apply vacuum to chamber A (outer chamber) and then to chamber B (inner chamber).

^ Monitor the ignition timing and compare to the chart. Increased vacuum should advance (increase) the crank angle.

^ Is the vacuum advance operating properly?

YES -- Check the vacuum hoses for leaks, cracks, and breakage. Repair as required. Return to Powertrain Management/System Diagnosis/Testing And Inspection Procedures.

NO -- Replace the vacuum diaphragm.