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* Check idle air control (DC) motor (if applicable). * Check idle air control (stepper) motor (if applicable). * Check for fuel injector malfunction. * Check for power transistor malfunction (if applicable). * Check A/C switch and power relay (if applicable). * Check for PCM malfunction. * Ensure electrical harness, connectors and wires are not broken, bent or loose. ENGINE SURGES * Check engine coolant temperature sensor. * Check EGR control solenoid valve (if applicable). * Check fuel pressure. * Check for fuel injector malfunction. DETONATION OR KNOCKING * Check for knock sensor malfunction (if applicable). * Check volume airflow sensor. * Check for engine cooling system problems. * Check fuel quality. * Check intake air temperature sensor. * Check barometric pressure sensor (if applicable). * Check manifold absolute pressure sensor (if applicable). * Check ignition coil. * Check power transistor (if applicable). * Check for EGR system malfunction. POOR FUEL MILEAGE * Check intake air temperature sensor. * Check engine coolant temperature sensor. * Check barometric pressure sensor (if applicable). * Check manifold absolute pressure sensor (if applicable). * Check ignition switch. * Check throttle position sensor. * Check camshaft position sensor. * Check crankshaft position sensor. * Check power steering oil pressure switch (if applicable). * Check A/C switch and power relay (if applicable). * Check park/neutral position switch (A/T). * Check heated oxygen sensor. * Check volume airflow sensor. * Check fuel pressure. * Check for SFI system malfunction. * Check idle air control (DC) motor (if applicable). * Check idle air control (stepper) motor (if applicable). * Check for fuel injector malfunction. * Check for power transistor malfunction (if applicable). INTERMITTENTS INTERMITTENT PROBLEM DIAGNOSIS Intermittent fault testing requires duplicating circuit or component failure to identify problem. These procedures may lead to computer setting a Diagnostic Trouble Code (DTC) which may help in diagnosis. If problem vehicle does not produce DTCs, monitor voltage or resistance values using a DVOM while attempting to reproduce conditions causing intermittent fault. A status change on DVOM |