Important Preliminary Inspections Before Starting

Before using the Symptom tables, perform the following:

Identifying Intermittent Conditions

Many intermittent conditions occur with harness or connector movement due to engine torque, rough pavement, vibration or physical movement of a component. Refer to the following for a list to help determine an intermittent condition:

If an intermittent is determined, refer to Testing for Intermittent Conditions and Poor Connections for specific strategies in diagnosing intermittent conditions.

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 stalls.

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
Find the symptom in the left column and perform the test/inspection procedure in the right column
•  Hard Start     •  Backfire	•  Symptoms - Fuel System     •  Symptoms - Ignition System     •  Symptoms - Sensors/Systems     •  Engine exhaust--Refer to Symptoms - Engine Exhaust .     •  Inspect the engine mechanical for oil consumption, correct engine compression and correct base engine timing--Refer to Symptoms - Engine Mechanical .     •  Backfire--Inspect the intake and exhaust system and associated passages for casting flash.     •  Inspect the engine cooling system for correct level and operation--Refer to Symptoms - Engine Cooling .     •  Inspect the engine electrical system for correct operation--Refer to Charging System Test .
Surges/Chuggles	•  Symptoms - Fuel System     •  Symptoms - Ignition System     •  Symptoms - Sensors/Systems     •  Inspect the engine mechanical for oil consumption, correct engine compression and correct base engine timing--Refer to Symptoms - Engine Mechanical .     •  Inspect the engine electrical system for correct operation--Refer to Charging System Test .     •  Engine exhaust--Refer to Restricted Exhaust .     •  Ensure the customer understands the operation of the Automatic Transmission including the Tap shift option if applicable.     •  HVAC System operation--Ensure the customer understands the operation of the HVAC system.
Lack of Power, Sluggishness, or Sponginess	•  Symptoms - Fuel System     •  Symptoms - Ignition System     •  Symptoms - Sensors/Systems     •  Inspect for a restricted air intake system.     •  Inspect for a dirty or restricted air filter.     •  Inspect the engine mechanical for oil consumption, correct engine compression and correct base engine timing--Refer to Symptoms - Engine Mechanical .     •  Inspect the engine electrical system for correct operation--Refer to Charging System Test .     •  Engine Exhaust--Refer to Restricted Exhaust .     •  Ensure the customer understands the operation of the Automatic Transmission including the Tap shift option if applicable.     •  Torque Management System, if applicable--Refer to ABS Description and Operation and Symptoms - Antilock Brake System .     •  HVAC System operation
•  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 restricted air intake system.     •  Inspect for a dirty or restricted air filter.     •  Inspect the engine mechanical for oil consumption, correct engine compression and correct base engine timing--Refer to Symptoms - Engine Mechanical .     •  Inspect the engine electrical system for correct operation--Refer to Charging System Test .     •  Engine Cooling System--Refer to Symptoms - Engine Cooling .     •  Engine Exhaust--Refer to Restricted Exhaust .     •  Inspect the engine mounts. Refer to Engine Mount Inspection .     •  Inspect the crankcase ventilation system--Refer to Crankcase Ventilation System Inspection/Diagnosis .     •  Inspect the air intake system for leaks and unmetered air     •  HVAC System operation     •  Inspect the automatic transmission for proper shifting and TCC engagement.
Detonation/Spark Knock	•  Excessive heavy loads or review owner's driving habits--Consult the Vehicle Owner's Manual.     •  Ensure quality fuel is used--Consult the Vehicle Owner's Manual     •  Symptoms - Fuel System     •  Symptoms - Ignition System     •  Inspect the engine mechanical for the following:        -  Oil consumption        -  Carbon build up or other hot point within the combustion chamber        -  Correct engine compression        -  Correct base engine timing        -  Refer to Symptoms - Engine Mechanical .     •  Engine Cooling System--Refer to Engine Overheating .     •  Inspect the automatic transmission for proper shifting and TCC engagement.
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     •  Inspect the engine mechanical for oil consumption, correct engine compression and correct base engine timing--Refer to Symptoms - Engine Mechanical .     •  Inspect the crankcase ventilation system--Refer to Crankcase Ventilation System Inspection/Diagnosis .     •  Inspect the engine cooling system for correct level and operation--Refer to Symptoms - Engine Cooling .     •  Engine Electrical System operation--Refer to Charging System Test .     •  Engine Exhaust--Refer to Symptoms - Engine Exhaust .     •  HVAC System operation--Ensure the customer understands the operation of the HVAC system     •  Ensure the customer understands the operation of the Automatic Transmission including the Tap shift option if applicable.     •  Inspect the Braking System--Refer to Brakes Drag .
Dieseling/Run-On	•  Symptoms - Fuel System     •  Symptoms - Ignition System     •  Inspect the engine mechanical for the following:        -  Carbon build up or other hot point within the combustion chamber        -  Correct engine compression        -  Correct base engine timing        -  Refer to Symptoms - Engine Mechanical .     •  Inspect the intake and exhaust system and associated passages for casting flash.