Hesitation, Sag, Stumble

DEFINITION
Momentary lack of response when 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).

POWERTRAIN SYSTEM CHECK
Perform Chart 1 Powertrain System Check. Chart 1 Powertrain System Check

FUEL SYSTEM CHECK
Perform Chart 6C-1 Fuel System Check. Check especially 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
- faulty Idle Speed Control (ISC) motor
- Sticking Throttle Position (TP) Switch

Chart 6C-1 Fuel System Check

IGNITION SYSTEM CHECKS
Perform Chart C-1 Ignition Control Performance Test. Check especially for:

^ High resistance, open, shorted, or arcing spark plug wires, crossfire between spark plug wires
^ Contaminated or damaged spark plugs
^ Distributor grounding points clean and tight
^ Correct ignition timing
^ Faulty ignition coil or Ignition Control (IC) module
^ Distributor cap, rotor, brush and button for moisture, cracks, dust or carbon tracking
^ Worn or loose distributor shaft gear
^ Bent distributor shaft or worn distributor shaft bushing

C Charts

EXHAUST GAS RECIRCULATION (EGR) SYSTEM CHECK
Perform Chart 6EC-2 EGR System Check. Chart 6EC-2 EGR System Check

MECHANICAL CAUSES
Check for the following mechanical causes:

^ Binding or sticking throttle linkage
^ Intake valve deposits
^ Valves sticking in valve guides
^ Vacuum leaks in intake manifold
^ Bent push rods
^ Worn rocker arms