Lack of Power/Sluggish/Spongy/Stumble

DEFINITION
Engine delivers less than expected power. Little or no increase in speed when accelerator is depressed part way.

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 in particular for:
^ Fuel Quality
- alcohol content
- low octane level
- contaminants
^ Incorrect fuel pressure
^ Plugged or dirty fuel filter
^ Fuel injectors
- incorrect flow rate

Chart 6C-1 Fuel System Check

IGNITION SYSTEM CHECK
Perform Chart C-1 Ignition Control Performance Test. Check in particular 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 SYSTEM
Perform exhaust diagnosis looking in particular for:

^ Restricted catalytic converter or exhaust

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:

^ Worn camshaft lobes
^ Bent push rods
^ Low engine compression
^ Broken or weak valve springs
^ Throttle not opening fully
^ Worn rocker arms
^ Restricted air induction flow
^ Vacuum leaks in intake manifold
^ Erratic Vehicle Speed Sensor (VSS) readings
^ Erratic engine RPM readings

DRIVER-INDUCED CAUSES
Check for possible driver-induced causes:

^ Vehicle displaying normal power