Important Preliminary Inspections Before Starting
Before using the Symptom tables, perform the following:
| - | Ensure that the engine control module (ECM) and malfunction indicator lamp (MIL) are operating correctly. |
| - | Ensure that there are no diagnostic trouble codes (DTCs) that are stored. |
| • | Verify the customer concern. |
| • | Perform the Visual/Physical Inspection in this section. The visual/physical inspection is extremely important, and can lead to correcting a condition without additional testing. It may also help reveal the cause of an intermittent condition. |
| • | Locate the correct symptom. Perform the tests and inspections associated with the symptom. |
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:
| • | Moisture and water intrusion in connectors, terminals, and components |
| • | High circuit or component resistance--High resistance can include any resistance, regardless of the amount, which can interrupt the operation of the component. |
| • | Harness that is located too tight, or chaffed circuits |
| • | High or low ambient temperature |
| • | High or low engine coolant temperatures |
| • | High underhood temperatures |
| • | Heat build up in component or circuit due to circuit resistance, poor terminal contact, or high electrical load |
| • | High or low system voltage |
| • | High vehicle load conditions |
| • | Electro-magnetic interference (EMI)/circuit interference from relays, solenoids or other electrical surge |
| • | Incorrect installation of non-factory, aftermarket, and after factory add on accessories |
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 PCM harness connectors |
| • | The electrical center fuse/relay cavities |
| • | The component terminals |
| • | The component harness connector |
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:
| • | Inspect vacuum hoses for splits, kinks, and proper connections, as shown on the Vehicle Emission Control Information label. Inspect thoroughly for any type of a leak or a restriction. |
| • | Inspect for a dirty or restricted air filter. |
| • | Inspect for water intrusion in the mass air flow (MAF)/intake air temperature (IAT) sensor connector, heated oxygen sensor (HO2S) connectors, control module connectors or any other harness connectors. |
| • | Inspect the air intake ducts, particularly between the MAF sensor and the throttle body for the following conditions: |
| • | Inspect for air leaks at the throttle body mounting area, the MAF sensor and intake manifold sealing surfaces. |
| • | Inspect the wiring harness for the following conditions: |
| • | Inspect for loose, damaged, unseated, or missing sensors/components. |
| • | Inspect terminals for corrosion and correct contact. |
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
|
|
|
Important: A vehicle with a camshaft actuator stuck in an un-parked position may experience a hard start.
Start and run the engine until fully warm. Observe the camshaft position (CMP) variation parameter while accelerating up to 1,500 RPM and back to idle several times. The CMP variation should indicate a value for 1-2 seconds and then
return to 0 degree. If the camshaft actuator does not respond, refer to
Camshaft Position Actuator Cleaning and Inspection
and
Camshaft Position Actuator Magnet Cleaning and Inspection
.
| • | 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. |
|
Surges/Chuggles
|
Important: A vehicle with a camshaft actuator uncontrolled and wandering may experience an engine surge.
Start and run the engine until fully warm. Observe the CMP variation parameter while accelerating up to 1,500 RPM and back to idle several times. The CMP variation should indicate a value for 1-2 seconds and then return to 0 degree.
If the camshaft actuator does not respond, refer to
Camshaft Position Actuator Cleaning and Inspection
and
Camshaft Position Actuator Magnet Cleaning and Inspection
.
| • | Inspect the engine mechanical for oil consumption, correct engine compression and correct base engine timing--Refer to
Symptoms - Engine Mechanical
. |
| • | Inspect the engine mechanical for correct engine oil pressure. Incorrect oil pressure may cause the camshaft actuator to vary beyond the device control when operated. Refer to
Oil Pressure Diagnosis and Testing
. |
| • | 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. Refer to the following: |
|
Lack of Power, Sluggishness, or Sponginess
|
Important: A vehicle with a camshaft actuator stuck in the park position may experience a lack of power during take off.
Start and run the engine until fully warm. Observe the CMP variation parameter while accelerating up to 1,500 RPM and back to idle several times. The CMP variation should indicate a value for 1-2 seconds and then return to 0 degree.
If the camshaft actuator does not respond, refer to
Camshaft Position Actuator Cleaning and Inspection
and
Camshaft Position Actuator Magnet Cleaning and Inspection
.
| • | 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 mechanical for correct engine oil pressure. Incorrect oil pressure may cause the camshaft actuator to vary beyond the device control when operated. Refer to
Oil Pressure Diagnosis and Testing
. |
| • | Ensure the customer understands the operation of the Automatic Transmission including the Tap shift option if applicable. |
| • | HVAC System operation--Refer to the following: |
|
Hesitation, Sag, Stumble
Cuts Out, Misses
Rough, Unstable, or Incorrect Idle and Stalling
|
Important: A rough idle may be considered a normal condition at start-up if the engine oil temperature is below -7°C (+19.4°F). This condition may last up to 200 seconds until the oil temperature warms enough
to allow stable operation of the camshaft actuator.
Important: A vehicle with a camshaft actuator stuck at full camshaft retard may experience a rough idle.
Start and run the engine until fully warm. Observe the CMP variation parameter while accelerating up to 1,500 RPM and back to idle several times. The CMP variation should indicate a value for 1-2 seconds and then return to 0 degree.
If the camshaft actuator does not respond, refer to
Camshaft Position Actuator Cleaning and Inspection
and
Camshaft Position Actuator Magnet Cleaning and Inspection
.
| • | Inspect for a restricted air intake system. |
| • | Inspect for a dirty or restricted air filter. |
| • | Ensure correct engine oil is used. Incorrect oil for the temperature may cause variations with camshaft actuator operation. |
| • | Inspect the intake manifold tuning valve for leaks at the seal and for proper operation. An uncontrolled tuning valve may cause isolations in the air flow-refer to intake manifold tuning valve inspection in the
Upper Intake Manifold Replacement
. |
| • | Inspect the engine mechanical for oil consumption, correct engine compression and correct base engine timing--Refer to
Symptoms - Engine Mechanical
. |
| • | Inspect the engine mechanical for correct engine oil pressure. Incorrect oil pressure may cause the camshaft actuator to vary beyond the device control when operated. Refer to
Oil Pressure Diagnosis and Testing
. |
| • | Inspect the air intake system for leaks and unmetered air |
| • | HVAC System operation--Refer to the following: |
|
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 |
| • | 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 |
|
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: |
| - | Fuel Service and Appearance Care in the vehicle Owner's Manual |
| • | Inspect the engine mechanical for oil consumption, correct engine compression and correct base engine timing--Refer to
Symptoms - Engine Mechanical
. |
| | Important: A vehicle with a camshaft actuator either stuck at full camshaft retard, in the park position, or uncontrolled and wandering may experience poor fuel economy.
|
| • | HVAC System operation. Ensure the customer understands the operation of the HVAC system--Refer to the following: |
| • | Ensure the customer understands the operation of the Automatic Transmission including the Tap shift option if applicable. |
|
Dieseling/Run-On
|
| • | 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 |
| • | Inspect the intake and exhaust system and associated passages for casting flash. |
|
