• HEADINGS
  • * PLEASE READ THIS FIRST *
  • ENGINE PERFORMANCE
• FIGURES
• TABLES
  • TUNE-UP TROUBLE SHOOTING
  • FUEL INJECTION TROUBLE SHOOTING

GENERAL INFORMATION

TROUBLE SHOOTING

* PLEASE READ THIS FIRST *

NOTE:

This article is generic in nature and all information does not apply to all vehicles. For vehicle specific information, see the appropriate articles in the ENGINE PERFORMANCE category.

ENGINE PERFORMANCE

NOTE:

This article is generic in nature and all information does not apply to all vehicles. For vehicle specific information, see the appropriate articles in the ENGINE PERFORMANCE category.

TUNE-UP TROUBLE SHOOTING

Problem & Possible Cause			Action
Carbon Fouled Plugs
Clogged Air Filter			Replace Air Filter
Incorrect Idle Speed			Reset Idle Speed
Faulty Ignition Wiring			Replace Ignition Wiring
Sticky Valves/Worn Valve Seal			Check Valve Train
Fuel Injection Operation			Check Fuel Injection
Wet/Oil Fouled Plugs
Worn Rings/Pistons			Overhaul/Replace Engine
Excessive Cylinder Wear			Overhaul/Replace Engine
Plug Gap Bridged
Combustion Chamber Carbon Deposits			Clean Combustion Chamber
Blistered Electrode
Engine Overheating			Check Cooling System
Loose Spark Plugs			Clean/Torque Plugs
Over-Advanced Timing			Reset Timing
Wrong Plug Heat Range			Install Correct Plug
Melted Electrodes
Incorrect Timing			Reset Timing
Burned Valves			Replace Valves
Engine Overheating			Check Cooling System
Wrong Plug Heat Range			Install Correct Plug
Engine Won't Start
Loose Connections			Check Connections
No Power			Check Fuses/Battery
Loose/Worn Timing Belt/Chain/Gears			Check Belt/Chain/Gears
Engine Runs Rough
Leaky/Clogged Fuel Injectors			Repair Fuel Injectors
Leaky/Clogged Fuel Lines			Repair Fuel Lines
Clogged Fuel Filter			Replace Fuel Filter
Incorrect Timing			Reset Timing/Check Advance
Faulty Plugs/Wires			Replace Plugs/Wires
Uneven Compression			Overhaul/Replace Engine
Poor Acceleration
Incorrect Ignition Timing			Reset Timing
Leaky Valves			Check Compression
Component Failure
Spark Arcing			Replace Faulty Part
Defective Pick-Up Coil			Replace Pick-Up Coil
Defective Ignition Coil			Replace Ignition Coil
Defective Control Unit			Replace Control Unit
Ignition Diagnosis By Scope Pattern
All Firing Lines Abnormally High
Retarded Ignition Timing			Reset Ignition Timing
Lean Air/Fuel Mixture			Adjust Fuel Mixture
High Secondary Resistance			Repair Secondary Ignition
All Firing Lines Abnormally Low
Rich Air/Fuel Mixture			Adjust Air/Fuel Mixture
Arcing Coil Wire			Replace Coil Wire
Cracked Coil			Replace Coil
Low Coil Output			Replace Coil
Low Compression			Check/Repair Engine
Several High Firing Lines
Fuel Mixture Unbalanced			Check Fuel System
EGR Valve Stuck Open			Clean/Replace EGR Valve
High Plug Wire Resistance			Replace Plug Wire
Cracked/Broken Plugs			Replace Plugs
Intake Vacuum Leak			Repair Leak
Several Low Firing Lines
Fuel Mixture Unbalanced			Adjust Fuel Mixture
Plug Wires Arcing			Replace Plug Wires
Cracked Coil Arcing			Replace Coil
Uneven Compression			Check/Repair Engine
Faulty Spark Plugs			Replace Plugs
Cylinders Not Firing
Cracked Distributor Cap			Replace Cap
Shorted Plug Wires			Replace Plug Wires
Mechanical Engine Fault			Check/Repair Engine
Spark Plugs Fouled			Replace Plugs
Carbon Track in Distributor Cap			Replace Cap
Hard Starting
Defective Ignition Coil(s)			Replace Coil(s)
Fouled Spark Plugs			Replace Plugs
Incorrect Timing			Reset Ignition Timing

NOTE:

This article is generic in nature and all information does not apply to all vehicles. For vehicle specific information, see the appropriate articles in the ENGINE PERFORMANCE category.

FUEL INJECTION TROUBLE SHOOTING

Problem & Possible Cause		Action
Cold Start Valve Inoperative		Test Cold Start Valve
Poor Vacuum/Electrical Connection		Repair Connections
Contaminated Fuel		Test Fuel for Water/Alcohol
Bad Fuel Pump Relay/Circuit		Test Relay/Wiring
Battery Voltage Low		Charge/Test Battery
Low Fuel Pressure		Test Press. Regulator/Pump
No Distributor Reference Pulse		Repair Ignition System
Coolant Temp. Sensor Defective		Test Temp. Sensor/Circuit
No Power To Injectors		Check Injector Fuse/Relay
Hard Starting
Defective Idle Air Control (IAC)		Test IAC and Circuit
EGR Valve Open		Test EGR Valve/Control Circuit
Restricted Fuel Lines		Inspect/Replace Fuel Lines
Poor MAP Sensor Signal		Test MAP Sensor/Circuit
Engine Stalls During Parking Maneuver		Check P.S. Press. Switch
Rough Idle
Dirty Fuel Injectors		Clean/Replace Injectors
Poor MAP Sensor Signal		Test MAP Sensor/Circuit
Intermittent Fuel Injector Operation		Check Harness Connectors
Erratic Vehicle Speed Sensor Inputs		Harness Too Close to Plug Wires
Poor O2 Sensor Signal		Test O2 Sensor/Circuit
Faulty PCV System		Check PCV Valve and Hoses
Poor Acceleration
Weak Fuel Pump		Replace Fuel Pump
Dirty Fuel Injectors		Clean/Replace Injectors
Excessive Intake Valve Deposits		Clean Intake System
Poor High Speed Operation
Low Fuel Pump Volume		Faulty Fuel Pump/Filter
Poor MAP Sensor Signal		Test Speed Sensor/Circuit
Acceleration Ping/Knock
Faulty EGR System		Check EGR Valve and Hoses
Poor Knock Sensor Signal		Test Knock Sensor/Circuit
Poor Baro Sensor Signal		Test Baro Sensor/Circuit
Improper Ignition Timing		Adjust Timing
Engine Overheating		Check Cooling System
Poor Quality Fuel		Use Different Fuel
Carbon Build-Up		Decarbon Engine