Hesitation, Sag, Stumble

Definition: Momentary lack of response as the accelerator is pushed down. Can occur at all vehicle speeds. Usually most severe when first trying to make the vehicle move, as from a stop sign. May cause engine to stall if severe enough.

PRELIMINARY CHECKS
^ Perform the careful visual/physical checks as described at start of "Symptoms".

SENSORS
^ CHECK: Throttle Position (TP) sensor Check TP sensor for binding or sticking. Voltage should increase at a steady rate as throttle is moved toward Wide Open Throttle (WOT).
^ CHECK: MAP sensor - use CHART C-1D.Chart C-1D Manifold Absolute Pressure (MAP) Output Check

IGNITION SYSTEM
^ CHECK: Spark plugs for being fouled or for faulty spark plug wire routing.
^ CHECK: Electronic ignition system ground, CKT 750.

FUEL SYSTEM
^ CHECK: Fuel pressure, use CHART A-7Related Tests, Information and Procedures.
^ CHECK: Contaminated fuel.
^ CHECK: EVAP canister purge system for proper operation. Use CHART C-3Chart C-3 Evaporative Emission Control System.
^ CHECK: Fuel injectors. Perform fuel injector coil/balance test, use CHART C-2A.Chart C-2A Fuel Injector Balance Test

ADDITIONAL CHECKS
^ CHECK: Service Bulletins for updates.
^ CHECK: EGR operation, use CHART C-7.Chart C-7 EGR System Check
^ CHECK: Engine thermostat functioning correctly and proper heat range.
^ CHECK: Generator output voltage. Repair if less than 9 volts or more than 16 volts.