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This Preliminary Information communication provides information to the technician on the steps to diagnose and repair vehicles that have check engine light and a misfire. Technician will find a P0300 set. If the misfiring cylinder is creating NO or very low power, technician will need to follow these diagnostics steps. 1) Swap the ignition coil and spark plug with another cylinder. 2) Inspect the plug when out for wet or dry condition. 3) Perform an injector test with a scan tool. 4) If the plug is wet then check for a leaking or stuck open injector. 5) If the plug is dry then enrich the intake air with propane. If the severity of the misfire is less with enrichment, suspect a weak or inoperative injector driver in the Engine Control Module and replace as needed. 6) Perform a cylinder leakage test to determine if there is a valve sealing concern. If there is a valve sealing concern see the latest version of PIP5029 for recommendations.

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Date Published
MAY 02, 2014
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