SPN 1324, FMI 11 - Misfire Detected Cylinder #2 Diagnostic Aids NOTE: If any other DTCs are present, diagnose those first. Oil Level- Many engines have valve trains that utilize lifters that are hydraulically actuated and require specific levels of oil to maintain proper pressure for lifter actuation. If the engine has improper oil, insufficient oil level, or has too much oil the hydraulic lifters may not function as intended causing changes in valve lift and timing. As a result, incomplete combustion may occur as a result of oil problems. Check engine oil level and oil type according to manufacture maintenance procedures. Fuel Level- Misfire can occur due to intermittent or prolonged loss of fuel pressure due to a lack of fuel supply. If misfire counts or faults set and a fuel pressure fault is not recorded, question the operator(s) about the possibility of running out of fuel before replacing components. Ignition System- Wear or damage to ignition system components (spark plugs, spark plug wires, distributor or ignition coils) can result in weak or misplaced spark causing partial combustion and thus partial misfire. o Spark Plug(s) – Check for fouled or damaged spark plugs. Replace and regap according to manufacture recommended procedure(s). o Spark Plug Wire(s) – Check that spark plug wire is properly connected to ignition coil and spark plug. If equipped, ensure that spark plug terminal nut is tight to plug and that there is not substantial wear on nut. Check for cracks in insulation of spark plug wire or boot. Replace spark plug wire(s) if deemed necessary according to manufacture recommended procedure(s). o Distributor modules- Check distributor for oxidized or corroded spark distribution conductors including the distributor rotor and distributor cap poles. Fuel Pressure – Check fuel rail pressure at key-on/engine-off or with External PowerAll On test running. Monitor fuel rail pressure when key is turned off to determine if fuel pressure bleeds down too quickly. Run an injector fire test on a couple of injectors to monitor the pressure drop in the rail for each injector. If an injector appears to flow inconsistent compared to others, replace and retest. Cylinder Check – Run a compression test and cylinder leak test on suspected cylinder(s) to check mechanical integrity of piston rings and valve seats. Exhaust Leak – Pressurize exhaust system with 1-2 psig of air and check for pressure leaks around exhaust manifold gasket and pre-catalyst EGO sensor. Replace gasket(s) and tighten fasteners according to manufacture recommended procedure(s).
Indmar Products
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All Rights Reserved Draft Rev. A-Jan. 2008
