Additional Symptoms Tests

Hard Start

• Verify that the engine coolant temperature (ECT) has not shifted in value. Refer to Temperature Versus Resistance .
• Verify the engine electrical system for correct operation. Refer to Symptoms - Engine Electrical .
• Verify that the driver is using the correct starting procedure as described in the owners manual.
• Verify that there is adequate fuel.
• Inspect for excessive crankshaft endplay that will cause the crankshaft position (CKP) sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Crankshaft and Bearing Cleaning and Inspection .
IMPORTANT: A vehicle with a camshaft actuator stuck in an unparked position may experience a hard start.
• Start and run the vehicle 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, 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 .

Hesitation, Sag, Stumble

• Inspect the mass air flow (MAF) sensor for obstruction, contamination, and damage. Refer to Throttle Body Assembly 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 (CKP) sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Crankshaft and Bearing Cleaning and Inspection .

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. Refer to Temperature Versus Resistance .
• Inspect the mass air flow (MAF) sensor for obstruction, contamination, and damage. Refer to Throttle Body Assembly Replacement .
• Inspect for foreign material accumulation in the throttle bore, and for carbon deposits on the throttle plate and shaft. Also inspect for throttle body tampering.
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.
• Start and run the vehicle 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, then return to 0 degree. If the camshaft actuator responds erratic, inconsistent, or not at all, refer to Camshaft Position Actuator Magnet Cleaning and Inspection and Camshaft Position Actuator Cleaning and Inspection .

Detonaton/Spark Knock

• Test for an engine overheating condition. Refer to Symptoms - Engine Cooling .
• Verify that the engine coolant temperature (ECT) has not shifted in value. Refer to Temperature Versus 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 Throttle Body Assembly Replacement .
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 vehicle 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, 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 .

Rough, Unstable, or Incorrect Idle and Stalling

• Inspect the mass air flow (MAF) sensor for obstruction, contamination, and damage. Refer to Throttle Body Assembly Replacement .
• Inspect the engine mounts. Refer to Engine Mount Inspection .
• 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 Throttle Body Assembly 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 ECM reduces the amount of fuel delivered to the engine, causing a driveability condition.
• Verify that each injector harness is connected to the correct injector.
IMPORTANT: 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 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, 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 .