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HESITATION, SAG, STUMBLE
Checks Action
DEFINITION: The engine has a momentary lack of response when accelerating the engine. The condi-
tion can occur at any engine speed. The condition may cause the engine to stall if it’s severe enough.
Preliminary Checks None.
Fuel System Checks
Check the fuel pressure. Refer to Fuel System Diagnosis.
Check for low fuel pressure during a moderate or full throttle accelera-
tion. If the fuel pressure drops below specification, there is possibly a
faulty low pressure regulator or a restriction in the fuel system.
Check the TMAP sensor response and accuracy.
Check Shut-Off electrical connections.
Check the Regulator, Venturi and Throttle body for proper installation
and leakage.
Ignition System Checks
NOTE: Natural Gas and Propane require higher secondary ignition system
voltages for the equivalent gasoline operating conditions.
Check for the proper ignition voltage output with J 26792 or the equiva-
lent. Verify that the spark plugs are the correct type and properly gapped.
Check for faulty spark plug wires.
Check for oil fouled spark plugs.
Additional Check
Check for manifold vacuum or air induction system leaks.
Check the alternator output voltage.
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