Important Preliminary Checks Before Starting

Before using the Symptom tables, use the following:

Locate the correct symptom in the list at the end of this section. Follow the procedures in the appropriate diagnostic table(s). Refer to Testing for Intermittent Conditions and Poor Connections if the condition is determined to be intermittent or cannot be duplicated.

Visual/Physical Check

Notice: Use the connector test adapter kit J 35616-A for any test that requires probing the following items:

•	The electrical center fuse/relay cavities

•	The component terminals

•	The component harness connector

Using this kit will prevent damage caused by the improper probing of connector terminals.

Several of the symptom procedures call for a careful visual and physical inspection. This can lead to correcting a condition without further tests and can save time. This inspection should include the following areas:

Symptoms

Hard Start:  Engine cranks OK, but does not start for a long time. Does eventually run, or may start, but immediately dies.

Surges/Chuggles: Engine power variation under steady throttle or cruise. Feels like the vehicle speeds up and slows down without a change in the accelerator pedal position.

Lack of Power, Sluggishness, or Sponginess: The engine delivers less than expected power. Little increase in speed, or a total lack of acceleration when the accelerator pedal is pushed down part way.

Detonation/Spark Knock: A mild to severe ping which usually occurs worse while under acceleration. The engine makes sharp metallic knocks that change with throttle opening.

Hesitation, Sag, Stumble: Momentary lack of response as the accelerator is pushed down. This condition can occur at any vehicle speed. This condition is usually more pronounced when first trying to make the vehicle move, as from a stop sign. This condition may cause the engine to stall if severe enough.

Cuts Out, Misses: A steady pulsation or jerking that follows engine speed, which is usually more pronounced as the engine load increases. This condition is not normally felt above 1,500 RPM or 48 km/h (30 mph). The exhaust has a steady spitting sound at idle or at low speed.

Poor Fuel Economy: Fuel economy, as measured by an actual road test, is noticeably lower than expected. Also, the fuel economy is noticeably lower than it was on this vehicle at one time, as previously shown by an actual road test.

Rough, Unstable, or Incorrect Idle and Stalling: The engine runs unevenly at idle. If severe, the engine or the vehicle may shake. Engine idle may vary in speed. Either condition may be severe enough to stall the engine.

Dieseling, Run-On: The engine continues to run after the key is turned OFF, but runs very rough. If the engine runs smooth, inspect the ignition switch and the ignition switch adjustment.

Backfire:  Fuel ignites in the intake manifold or in the exhaust system, making a loud popping noise.

Use the following symptoms in order to isolate possible systems that are associated with the condition:

Symptoms

Symptoms	Action/System
Hard Start Backfire	•  Symptoms - Fuel System     •  Symptoms - Ignition System     •  Symptoms - Sensors/Systems     •  Engine Exhaust--Refer to Restricted Exhaust .     •  Engine Mechanical--Refer to Symptoms - Engine Mechanical .     •  Engine Cooling System--Refer to Engine Overheating or Thermostat Diagnosis .     •  Engine Electrical System operation--Refer to Charging System Test .     •  Manual Transmission--Refer to Symptoms - Manual Transmission .
Surges/Chuggles	•  Symptoms - Sensors/Systems     •  Symptoms - Ignition System     •  Symptoms - Fuel System     •  Engine Mechanical--Refer to Symptoms - Engine Mechanical .     •  Engine Electrical System operation--Refer to Charging System Test .     •  Engine Exhaust--Refer to Restricted Exhaust .     •  Manual Transmission--Refer to Symptoms - Manual Transmission .     •  HVAC System operation--Refer to the following:        -  Air Conditioning (A/C) System Performance Test        -  Symptoms - HVAC Systems - Automatic        -  Symptoms - HVAC Systems - Automatic
Lack of Power, Sluggishness, or Sponginess	•  Symptoms - Fuel System     •  Symptoms - Ignition System     •  Symptoms - Sensors/Systems     •  Inspect for a dirty or restricted air filter.     •  Engine Mechanical--Refer to Symptoms - Engine Mechanical .     •  Engine Electrical System operation--Refer to Charging System Test .     •  Engine Exhaust--Refer to Restricted Exhaust .     •  HVAC System operation--Refer to the following:        -  Air Conditioning (A/C) System Performance Test        -  Symptoms - HVAC Systems - Automatic        -  Symptoms - HVAC Systems - Automatic     •  Manual Transmission--Refer to Symptoms - Manual Transmission .     •  Torque Management System, if applicable--Refer to ABS Description and Operation and Symptoms - Antilock Brake System .
Hesitation, Sag, Stumble Cuts Out, Misses Rough, Unstable, or Incorrect Idle and Stalling	•  Symptoms - Fuel System     •  Symptoms - Ignition System     •  Symptoms - Sensors/Systems     •  Inspect for a dirty or restricted air filter.     •  Engine Mechanical--Refer to Symptoms - Engine Mechanical .     •  Inspect the positive crankcase ventilation (PCV) System.     •  Inspect the air intake system for leaks and unmetered air.     •  Engine Electrical System operation--Refer to Charging System Test .     •  Engine Cooling System--Refer to Symptoms - Engine Cooling .     •  HVAC System operation--Refer to the following:        -  Air Conditioning (A/C) System Performance Test        -  Symptoms - HVAC Systems - Automatic        -  Symptoms - HVAC Systems - Automatic     •  Manual Transmission--Refer to Symptoms - Manual Transmission .
Detonation/Spark Knock	•  Excessive heavy loads or owner driving habits--Consult the Vehicle Owner's Manual.     •  Symptoms - Fuel System     •  Symptoms - Ignition System     •  Engine Mechanical--Refer to Symptoms - Engine Mechanical .     •  Engine Cooling System--Refer to Engine Overheating .     •  Manual Transmission--Refer to Symptoms - Manual Transmission .
Poor Fuel Economy	•  Proper tire inflation--Refer to Tires in Service and Appearance Care in the vehicle Owner's Manual.     •  Inspect for a dirty or restricted air filter.     •  Fuel Quality--Refer to the following:        -  Alcohol/Contaminants-in-Fuel Diagnosis        -  Fuel Service and Appearance Care in the vehicle Owner's Manual     •  Symptoms - Fuel System     •  Symptoms - Ignition System     •  Symptoms - Sensors/Systems     •  Engine Mechanical--Refer to Symptoms - Engine Mechanical .     •  Inspect the PCV System.     •  Engine Cooling--Refer to Thermostat Diagnosis .     •  Engine Electrical System operation--Refer to Charging System Test .     •  Engine Exhaust--Refer to Restricted Exhaust .     •  HVAC System operation--Refer to the following:        -  Air Conditioning (A/C) System Performance Test        -  Symptoms - HVAC Systems - Automatic        -  Symptoms - HVAC Systems - Automatic     •  Manual Transmission--Refer to Symptoms - Manual Transmission .     •  Braking System--Refer to Hydraulic Brake System Diagnosis .
Dieseling/Run-On	•  Symptoms - Fuel System     •  Symptoms - Ignition System     •  Engine Mechanical--Refer to Symptoms - Engine Mechanical .