Additional Symptoms Tests: Notes

Hard Start

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 .
Test the engine coolant temperature (ECT) sensor. Compare the ECT sensor value to the intake air temperature (IAT) sensor value on a cold engine. The ECT and IAT sensor values should be within ± 3°C (5°F). If the ECT sensor is out of range with the IAT sensor, test the resistance of the ECT sensor. Refer to 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 (LF1) . If the sensor is within the specification, test the ECT sensor circuits for high resistance.
Verify that the fuel system has adequate pressure for engine start-up. With a scan tool, compare the Fuel Pressure Sensor parameter value to the Desired Fuel Pressure parameter value when the ignition key is first turned to ON. Refer to Fuel System Diagnosis .
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 .

Hesitation, Sag, Stumble

Test the fuel pressure. Refer to 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 .
Test the generator. Refer to Symptoms - Engine Electrical . Repair the charging system if the generator output voltage is less than 9 volts or more than 16 volts.
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 .
Test the manifold absolute pressure (MAP) sensor. Refer to DTC P0106 (LF1) .

NOTE: The following actions may need to be repeated in order to verify an intermittent intake or exhaust camshaft actuator condition.

Engine warm and idling, verify the correct operation of the camshaft actuator system. Command the intake and exhaust camshaft actuators from 0 degrees to 25 degrees and back to zero while observing the scan tool Intake Camshaft Position Variance and Exhaust Camshaft Position Variance parameters. Each parameter should be less than 2 degrees in each of the commanded states.
- If any of the parameters is greater than 2 degrees, inspect the suspect camshaft actuator and camshaft actuator solenoid valve and valve bore for contamination, obstruction, and damage. Refer to Camshaft Position Actuator Solenoid Valve Replacement and Camshaft Actuator System Description .

Poor Fuel Economy

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 (LF1,LFW) or Engine Control Module Scan Tool Information (LAF) 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 for resistance specifications. Replace the ECT sensor if the resistance is not within specification. Refer to Engine Coolant Temperature Sensor Replacement (LF1) . 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 .
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 .

Detonaton/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 .
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 (LF1,LFW) or Engine Control Module Scan Tool Information (LAF) 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 for resistance specifications. Replace the ECT sensor if the resistance is not within specification. Refer to Engine Coolant Temperature Sensor Replacement (LF1) . 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, Hesitation, or Cut Out

Inspect the engine electrical system for correct operation. Refer to 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 .

NOTE: The following actions may need to be repeated in order to verify an intermittent intake or exhaust camshaft actuator condition.

Engine warm and idling, verify the correct operation of the camshaft actuator system. Command the intake and exhaust camshaft actuators from 0 degrees to 25 degrees and back to zero while observing the scan tool Intake Camshaft Position Variance and Exhaust Camshaft Position Variance parameters. Each parameter should be less than 2 degrees in each of the commanded states.
- If any of the parameters is greater than 2 degrees, inspect the suspect camshaft actuator and camshaft actuator solenoid valve and valve bore for contamination, obstruction, and damage. Refer to Camshaft Position Actuator Solenoid Valve Replacement and Camshaft Actuator System Description .

Rough, Unstable, or Incorrect Idle and Stalling

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 .
Inspect the mass air flow (MAF) sensor for obstruction, contamination, and damage. Refer to Mass Airflow Sensor with Intake Air Temperature Sensor Replacement .
Inspect the engine mounts.
Inspect the intake and exhaust manifolds for casting flash.

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 .
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.

Fuel Odor

Saturated EVAP canister-Refer to Evaporative Emission Control System Description .
A condition with the internal components of the fuel tank assembly-Refer to Fuel System Description (LF1) .
Inspect for damaged or deteriorated fuel lines.