Hesitation, Sag, Stumble

DEFINITION
Momentary lack of response as the Accelerator is pushed down. Can occur at all car speeds. Usually most severe when first trying to make the car move, as from a stop sign. May cause Engine to stall if severe enough.

PRELIMINARY CHECKS
Perform the careful Visual/Physical Checks as described in Preliminary Checks. Preliminary Checks

SENSORS
CHECK: Throttle Position Sensor for binding or sticking. Voltage should increase at a steady rate as Throttle is moved toward Wide Open Throttle.
CHECK: Manifold Absolute Pressure Sensor. See Diagnostic Charts / Chart C-1D. C-1D ~ Manifold Absolute Pressure Sensor (MAP)

FUEL SYSTEM
CHECK: Fuel Pressure, See Diagnostic Charts / Chart A-7. A - Charts
CHECK: Fuel Injectors are correct for Vehicle.
CHECK: Contaminated Fuel.
CHECK: Evaporative Emission Canister Purge System for proper operation. Refer to Diagnostic Charts / Chart C-3. C-3 ~ Evaporative Emission Canister (EVAP)

IGNITION SYSTEM
CHECK: Spark Plugs for being fouled, or for faulty secondary wiring.
CHECK: Ignition timing, using a "Scan Tool".
CHECK: Ignition System ground.

ADDITIONAL CHECKS
CHECK: Exhaust Gas Recirculation operation, see Diagnostic Charts / Chart C-7. C-7A ~ EGR System Check
CHECK: Engine Thermostat functioning correctly and proper heat range.
CHECK: Generator output voltage. Repair if less than 9 or more than 16 volts.