Hesitation, Sag, Stumble

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 the engine to stall if severe enough.



PRELIMINARY CHECKS

^ Perform the careful visual/physical checks as described at start of "Symptoms".



ADDITIONAL CHECKS

^ CHECK: For correct PROM or ECM (see Service Bulletins).

^ CHECK: Generator output voltage. Repair, if less than 9 or more than 16 volts.

^ CHECK: EGR valve operation use CHART C-7.



FUEL SYSTEM

CHECK: 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).

^ CHECK: MAP sensor response and accuracy - Use CHART C-1D.



IGNITION SYSTEM

^ CHECK: Spark plug wires for being faulty.

^ CHECK: Spark plugs for being fouled.

^ CHECK: Ignition system for moisture, dust, cracks, burns, etc.

^ CHECK: Open ignition system ground.

^ CHECK: Ignition timing. See "Vehicle Emission Control Information" label.