Hesitation, Sag, Stumble

DEFINITION
Momentary lack of response as the accelerator is pushed down. Can occur at all vehicle speeds. Usually more 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 check as described in Preliminary Checks.

SENSORS
Check:
Throttle Position (TP) sensor - Check TP sensor for binding or sticking, TP sensor signal voltage should increase at a steady rate as throttle is moved toward Wide Open Throttle (WOT).
Manifold Absolute Pressure (MAP) sensor.

FUEL SYSTEM
Check:
Fuel pressure, use Chart A-7. Testing and Inspection
Contaminated fuel. Verify proper fuel usage with manufacturer recommended minimum ratingof9i octane.
Evaporative Emission (EVAP) control system for proper operation, use Chart C-3. Testing and Inspection
Fuel injectors. Perform injector balance test, use Chart C-2A. Testing and Inspection

IGNITION SYSTEM
Check:
Spark plugs for being fouled or for faulty secondary ignition wires for an open or short.
For proper ignition voltage output using spark tester J 26794 (ST 125) or equivalent.
Ignition Control (IC) system ground, CKT 251.

ADDITIONAL CHECKS
Check:
For correct Programmable Read Only Memory (PROM). (Refer to Service Bulletins.)
Engine thermostat functioning correctly and proper heat range.
Generator output voltage. Repair if less than 9 or more than 17.3 volts.
Exhaust Gas Recirculation (EGR) operation, use Chart C-7. Testing and Inspection
Air induction system for restriction or leaks.