Hesitation, Sag, Stumble

SYMPTOM 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
^ Refer to Diagnostic Notes. Initial Inspection and Diagnostic Overview

FUEL SYSTEM
Check:
^ Fuel pressure.
^ 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).
^ MAP sensor response and accuracy. Refer to "Manifold Absolute Pressure (MAP) Output Check." MAP Sensor Output Diagnosis
^ Water/contaminated fuel.
^ Canister purge system for proper operation.

IGNITION SYSTEM
Check:
^ Spark plug wires for being faulty.
^ Spark plugs for being fouled.
^ Open ignition system ground CKT 453 or ignition timing.

ADDITIONAL CHECKS
Check:
^ Service Bulletins for PROM updates.
^ Generator output voltage. Repair if less than 9 or more than 16 volts.
^ EGR valve operation.