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 in Preliminary Checks.
- For correct PROM.
- Service Bulletins for updates.
- Exhaust Gas Recirculation (EGR) operation, use Chart-C7. Testing and Inspection

SENSOR CHECKS
- Throttle Position (TP) sensor - For binding or sticking. Voltage should increase at a steady rate as throttle is moved toward Wide Open Throttle (WOT).
- Manifold Absolute Pressure (MAP) sensor, use Chart C-1D. Testing and Inspection

IGNITION SYSTEM CHECKS
- Spark plugs for being fouled.
- Ignition system ground.

FUEL SYSTEM CHECKS
Fuel pressure, use CHART A-7. Testing and Inspection
- Contaminated fuel.
- Evaporative Emissions (EVAP) canister purge system for proper operation. Use CHART C-3. Testing and Inspection
- Fuel injectors. Perform injector balance test, use CHART C-2A. Testing and Inspection

ADDITIONAL CHECKS
- Engine thermostat functioning correctly and proper heat range.
- Generator output voltage. Repair if less than 10 or more than 16 volts.
- Intake valve deposits.