Hesitation, Sag, Stumble

DEFINITION:
Momentary lack of response as the accelerator is depressed. The problem can occur at all vehicle speeds. Usually most severe when accelerating from a stop, and may cause the engine to stall. Usually caused by a lean condition (not enough fuel),

Check Powertrain System, if not already completed

Check Fuel System, looking in particular for:

- Fuel Quality:
- Alcohol Content
- Contaminants
- Water Content
- Sour Fuel

- Low Fuel Pressure

- Fuel injectors:
- Not Operating
- Low Flow Rate


- Plugged or dirty Fuel Filter

- Idle Speed Control:
- Binding ISC Motor
- Sticking TP Switch



Check Ignition System, looking in particular for:

- High Resistance, Open, Shorted, or Arcing Spark Plug Wires, crossfire between spark plug wires

- Contaminated or Damaged Spark Plugs

- Faulty Coil Pack or IC Module



Check EGR System.

Check for the following mechanical causes:

- If "Traction Control" telltale is on when the condition occurs, Check Traction Control Operation.

- Binding or Sticking Throttle Linkage

- Intake Valve Deposits

- Valves Sticking in Guides

- Improper Camshaft Timing

- Vacuum Leaks in Intake Manifold System