Additional Symptoms Tests

Detonation/Spark Knock

Test the engine for an overheating condition. Refer to Symptoms - Engine Cooling .

Poor Fuel Economy

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.

Rough, Unstable, or Incorrect Idle and Stalling

Inspect the engine mounts.

Surges/Chuggles

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.

Hard Start (without Fuel Pump Control Module)

• 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 for resistance specifications. Replace the ECT sensor if the resistance is not within specification. Refer to Engine Coolant Temperature Sensor Replacement . If the sensor is within the specification, test the ECT circuits for a high resistance.
• Test the idle air control (IAC) system.
• Test the fuel pump relay operation. The fuel pump should turn ON for 2 seconds when the ignition is turned ON. Refer to Fuel System Diagnosis (Without FPCM)  or Fuel System Diagnosis (FPCM) .

Hard Start (with Fuel Pump Control Module)

• Test the ECT sensor. Compare the ECT sensor value to the 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 for resistance specifications. Replace the ECT sensor if the resistance is not within specification. Refer to Engine Coolant Temperature Sensor Replacement . If the sensor is within the specification, test the ECT circuits for a high resistance.
• Test the IAC system.
• Verify that the fuel system has adequate pressure for engine start-up. Refer to Fuel System Diagnosis (Without FPCM)  or Fuel System Diagnosis (FPCM)  for fuel pressure specifications.

Hesitation, Sag, Stumble

• Test the manifold absolute pressure (MAP) sensor. Refer to DTC P0106 .
• 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.

Poor Fuel Economy

• Heavy loads being carried or towed.
• Acceleration rate too much or too often.
• 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.