Hesitation, Sag, Stumble

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

PRELIMINARY CHECKS
- Perform the careful visual/physical checks.

SENSORS
Check the following:
- Throttle Position Sensor for binding or sticking. Voltage should increase at a steady rate as throttle is moved toward Wide Open Throttle.
- Manifold Absolute Pressure sensor, chart C-1D.

FUEL SYSTEM
Check the following:
- Fuel pressure, chart A-7.
- Fuel injectors are correct for vehicle.
- Contaminated fuel.
- Evaporative Emission Canister Purge system for proper operation.

IGNITION SYSTEM
Check the following:
- Spark plugs for being fouled, or for faulty secondary wiring.
- Ignition timing, using a "Scan Tool".
- Ignition system ground.

ADDITIONAL
Check the following:
- Exhaust gas recirculation operation, chart C-7.
- Engine thermostat functioning correctly and proper heat range.
- Generator output voltage. Repair if less than 9 or more than 16 volts.