Hesitation, Sag, Stumble. GMC Truck Safari

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2002 🢒 Safari - 2WD 🢒 Engine 🢒 Engine Electrical 🢒 Hesitation, Sag, Stumble

Inspections

Action

DEFINITION: The vehicle has a momentary lack of response when depressing the accelerator. The condition can occur at any vehicle speed. The condition is usually most severe when trying to make the vehicle move, as from a stop sign. The condition may cause the engine to stall if the condition is severe enough.

Preliminary

Refer to Symptoms - Engine Controls .

Fuel System

•	Test the fuel pressure. Refer to Fuel System Diagnosis .

•	Inspect the throttle position (TP) sensor for binding or sticking. TP voltage should increase at a steady rate as the throttle moves toward wide open throttle (WOT).

•	Inspect for water contamination in the fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

•	Test the canister purge system for proper operation. Refer to Service Bay Test .

•	Perform the fuel injector coil test. Refer to Fuel Injector Solenoid Coil Test .

•	Perform the fuel injector balance test. Refer to Fuel Injector Balance Test with Tech 2 .

•	Test for low fuel pressure after a cold start or during a moderate or full throttle acceleration. Refer to Fuel Pressure Gage Installation and Removal .

Ignition System

•	Inspect for damaged spark plug wires. Refer to Spark Plug Wire Inspection .

•	Inspect for fouled spark plugs. Refer to Spark Plug Inspection .

•	Inspect for proper ignition system performance. Refer to Distributor Ignition (DI) System Diagnosis .

Additional

•	Review the Service Bulletins for calibration updates.

•	Test the generator output voltage. Refer to Diagnostic System Check - Engine Electrical in Engine Electrical.

•	Inspect for a restricted exhaust. Refer to Restricted Exhaust in Engine Exhaust.