Symptoms - Engine Controls Part 2
Symptoms - Engine Controls
Hesitation, Sag, Stumble - With RPO LF1
* Test the fuel pressure. Refer to Fuel System Diagnosis (Fuel System Diagnosis).
* Inspect the mass air flow (MAF) sensor for obstruction, contamination, and damage. Refer to Mass Airflow Sensor with Intake Air Temperature Sensor Replacement (Service and Repair).
* Test the generator. Refer to Symptoms - Engine Electrical (Symptoms - Engine Electrical). Repair the charging system if the generator output voltage is less than 9 V or more than 16 V.
* Inspect for excessive crankshaft endplay that will cause the crankshaft position sensor reluctor wheel to move out of alignment with the crankshaft position sensor. Refer to Crankshaft and Bearing Cleaning and Inspection (52. Crankshaft and Bearing Cleaning and Inspection).
* Test the manifold absolute pressure (MAP) sensor.
Poor Fuel Economy - With RPO LLT
* Heavy loads being carried or towed
* Acceleration rate too much or too often
* Inspect the brake system for brake drag.
* Inspect for incorrect operation of the speedometer.
* Verify that the engine coolant temperature (ECT) has not shifted in value. Allow the engine to run and reach operating temperature. Observe the ECT Sensor parameter with a scan tool and compare the reading to that parameter listed on the Engine Control Module Scan Tool Information (V6) (Scan Tool Testing and Procedures) list. If the reading is not in the range specified in the list, test the resistance of the ECT sensor. Refer to Temperature Versus Resistance - Engine Coolant Temperature Sensor (Temperature Versus Resistance - Engine Coolant Temperature Sensor) for resistance specifications. Replace the ECT sensor if the resistance is not within specification. Refer to Engine Coolant Temperature Sensor Replacement (LLT) (Service and Repair). If the sensor is within the specification, test the ECT sensor circuits for high resistance.
* Inspect the mass air flow (MAF) sensor for obstruction, contamination, and damage. Refer to Mass Airflow Sensor with Intake Air Temperature Sensor Replacement (Service and Repair).
* Inspect the throttle body and clean if necessary. Refer to Throttle Body Inspection and Cleaning (Procedures).
Note: A vehicle with a camshaft actuator either stuck at full camshaft retard, in the parked position, or uncontrolled and wandering may experience poor fuel economy.
* Start and run the vehicle until fully warm. Observe the CMP Bank 1 and Bank 2 Variance parameters while accelerating up to 1,500 RPM and back to idle several times. The CMP parameters should indicate a value for 1-2 s, then return to 0 degree. If the camshaft actuator does not respond, refer to Camshaft Actuator System Description (Camshaft Actuator System).
Poor Fuel Economy - With RPO LF1
* Heavy loads being carried or towed
* Acceleration rate too much or too often
* Inspect the brake system for brake drag.
* Inspect for incorrect operation of the speedometer.
* Verify that the engine coolant temperature (ECT) has not shifted in value. Allow the engine to run and reach operating temperature. Observe the ECT Sensor parameter with a scan tool and compare the reading to that parameter listed on the Engine Control Module Scan Tool Information (V6) (Scan Tool Testing and Procedures) list. If the reading is not in the range specified in the list, test the resistance of the ECT sensor. Refer to Temperature Versus Resistance - Engine Coolant Temperature Sensor (Temperature Versus Resistance - Engine Coolant Temperature Sensor) for resistance specifications. Replace the ECT sensor if the resistance is not within specification. Refer to Engine Coolant Temperature Sensor Replacement (LLT) (Service and Repair). If the sensor is within the specification, test the ECT sensor circuits for high resistance.
* Inspect the mass air flow (MAF) sensor for obstruction, contamination, and damage. Refer to Mass Airflow Sensor with Intake Air Temperature Sensor Replacement (Service and Repair).
* Observe the Throttle Body Idle Airflow Compensation parameter with a scan tool. A value greater than 80 % may indicate an excessive accumulation of deposits in the throttle bore. Inspect the throttle body and clean, if necessary. Refer to Throttle Body Inspection and Cleaning (Procedures).
Note: A vehicle with a camshaft actuator either stuck at full camshaft retard, in the parked position, or uncontrolled and wandering may experience poor fuel economy.
* Start and run the vehicle until fully warm. Observe the CMP Bank 1 and Bank 2 Variance parameters while accelerating up to 1,500 RPM and back to idle several times. The CMP parameters should indicate a value for 1-2 s, then return to 0 degree. If the camshaft actuator does not respond, refer to Camshaft Actuator System Description (Camshaft Actuator System).
Detonation/Spark Knock
* Inspect for excessive carbon buildup in the combustion chambers. Clean the chambers with Top Engine Cleaner. Follow the instructions on the can.
* Test for an engine overheating condition. Refer to Engine Overheating (Engine Overheating).
* Verify that the engine coolant temperature (ECT) has not shifted in value. Allow the engine to run and reach operating temperature. Observe the ECT Sensor parameter with a scan tool and compare the reading to that parameter listed on the Engine Control Module Scan Tool Information (V6) (Scan Tool Testing and Procedures) list. If the reading is not in the range specified in the list, test the resistance of the ECT sensor. Refer to Temperature Versus Resistance - Engine Coolant Temperature Sensor (Temperature Versus Resistance - Engine Coolant Temperature Sensor) for resistance specifications. Replace the ECT sensor if the resistance is not within specification. Refer to Engine Coolant Temperature Sensor Replacement (LLT) (Service and Repair). If the sensor is within the specification, test the ECT sensor circuits for high resistance.
* If there are no engine mechanical faults, fill the fuel tank with a known high quality fuel that meets the vehicle minimum octane requirements.
Lack of Power, Sluggishness, or Sponginess
* Inspect the engine electrical system for correct operation. Refer to Symptoms - Engine Electrical (Symptoms - Engine Electrical).
* Verify that each injector harness is connected to the correct injector.
* Inspect the mass air flow (MAF) sensor for obstruction, contamination, and damage. Refer to Mass Airflow Sensor with Intake Air Temperature Sensor Replacement (Service and Repair).
Note: A vehicle with a camshaft actuator stuck in the Park position may experience a lack of power during take-off.
* Start and run the vehicle until fully warm. Observe the CMP Bank 1 and Bank 2 Variance parameters while accelerating up to 1,500 RPM and back to idle several times. The CMP parameters should indicate a value for 1-2 s, then return to 0 degree. If the camshaft actuator does not respond, refer to Camshaft Actuator System Description (Camshaft Actuator System).
Rough, Unstable, or Incorrect Idle and Stalling - With RPO LLT
* Inspect the throttle body and clean, if necessary. Refer to Throttle Body Inspection and Cleaning (Procedures).
* Inspect the mass air flow (MAF) sensor for obstruction, contamination, and damage. Refer to Mass Airflow Sensor with Intake Air Temperature Sensor Replacement (Service and Repair).
* Inspect the engine mounts.
* Inspect the intake and exhaust manifolds for casting flash.
Note: The ECM uses the cylinder 1 intake camshaft position sensor to determine injector and ignition system synchronization, as well as to determine camshaft to crankshaft relationship. If the cylinder 1 intake camshaft position sensor signal to the ECM is intermittent, a stalling condition will occur and a DTC will not set.
* Inspect all cylinder 1 intake camshaft position sensor wiring for poor connections. Start the engine and observe for engine stalling while wiggling the cylinder 1 intake camshaft position sensor wiring harness. Refer to Inducing Intermittent Fault Conditions (Inducing Intermittent Fault Conditions) for further diagnosis.
Rough, Unstable, or Incorrect Idle and Stalling - With RPO LF1
* Observe the Throttle Body Idle Airflow Compensation parameter with a scan tool. A value greater than 80 % may indicate an excessive accumulation of deposits in the throttle bore. Inspect the throttle body and clean, if necessary. Refer to Throttle Body Inspection and Cleaning (Procedures).
* Inspect the mass air flow (MAF) sensor for obstruction, contamination, and damage. Refer to Mass Airflow Sensor with Intake Air Temperature Sensor Replacement (Service and Repair).
* Inspect the engine mounts.
* Inspect the intake and exhaust manifolds for casting flash.
Note: The ECM uses the cylinder 1 intake camshaft position sensor to determine injector and ignition system synchronization, as well as to determine camshaft to crankshaft relationship. If the cylinder 1 intake camshaft position sensor signal to the ECM is intermittent, a stalling condition will occur and a DTC will not set.
* Inspect all cylinder 1 intake camshaft position sensor wiring for poor connections. Start the engine and observe for engine stalling while wiggling the cylinder 1 intake camshaft position sensor wiring harness. Refer to Inducing Intermittent Fault Conditions (Inducing Intermittent Fault Conditions) for further diagnosis.
Surges/Chuggles
* Inspect the mass air flow (MAF) sensor for obstruction, contamination, and damage. Refer to Mass Airflow Sensor with Intake Air Temperature Sensor Replacement (Service and Repair).
* Test the heated oxygen sensors (HO2S). The HO2S should respond quickly to a change in throttle position. If the HO2S do not respond to different throttle positions, inspect for contamination from fuel, silicon, or the incorrect use of RTV sealant. The sensors may have a white powdery coating and result in a high, but false, signal voltage, which gives a rich exhaust indication. The PCM reduces the amount of fuel delivered to the engine, causing a driveability condition.
* Verify that each injector harness is connected to the correct injector.
Note: A vehicle with a camshaft actuator uncontrolled and wandering may experience an engine surge.
* Start and run the vehicle until fully warm. Observe the CMP Bank 1 and Bank 2 Variance parameters while accelerating up to 1,500 RPM and back to idle several times. The CMP parameters should indicate a value for 1-2 s, then return to 0 degree. If the camshaft actuator does not respond, refer to Camshaft Actuator System Description (Camshaft Actuator System).
Fuel Odor
* Saturated EVAP canister-Refer to Evaporative Emission Control System Description (Evaporative Emission Control System Description).
* A condition with the internal components of the fuel tank assembly-Refer to Fuel System Description (LLT) (Fuel System Description).
* Inspect for damaged or deteriorated fuel lines.
ECM Commanded Reduced Engine Power
Review the Reduced Engine Power Indication History parameter with a scan tool to determine the reason for the last reduced engine power event.