VPA 7743722 English 10-2004 107
Troubleshooting
Engine Runs Rough
If Fuel Injected, see EFI Di-
agnostic Manual
If At Slow Speed - Check:
Idle speed and idle mixture.
Engine timing and spark plugs.
Fuel pump pressure.
Water or contaminants in fuel.
Carburetor or manifold vacuum leak.
Internal carburetor fuel leak.
See Electrical/Ignition/Fuel Service Manual.
If At High Speed - Check:
Air leak on suction side of fuel system.
Too low octane fuel.
Ignition system secondary circuit.
Engine timing.
Wrong model or size carburetor, improper main jets or power valve,
defective secondary fuel circuit, or secondary vacuum diaphragm
failure.
External canister and carburetor fuel filters.
Fuel pump pressure.
Engine compression.
Water or contaminants in fuel, or water in cylinders.
See General Information on page 17 and the Electrical/Ignition/Fuel
System Service Manual.
Engine Noises and
Vibrations
Valves - Hydraulic Lifters
Rapping only when starting–oil too heavy for prevailing weather, var-
nish on lifter, oil needs to be changed.
Intermittent rapping–leakage at lifter check ball.
Idle noise–excessive leak down rate, faulty check ball seat.
Generally noisy–excessive oil in crankcase, stuck lifter plunger.
Loud noise at operating temperature–scored lifter plunger, fast leak
down rate, oil viscosity too light for prevailing weather or operating
temperatures.
See appropriate Engine section.
Ignition System (Ping or Knock)
Improper tuning.
Incorrect spark plug wire routing.
Use higher octane fuel.
See Electrical/Ignition/Fuel Service Manual.
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