Possible Causes & Corrections

Check the following items:

• Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter. See EXHAUST SYSTEM BACKPRESSURE under MECHANICAL INSPECTION in appropriate BASIC DIAGNOSTIC PROCEDURES article.
• Check ignition system for bare or shorted spark plug wires, loose ignition coil connections. Check for shorts by misting plug wires with water.
• Check ignition system for faulty grounds.
• Using Spark Tester (J-26792), check for adequate spark output.
• Remove spark plugs. Check for wet/fouled spark plugs, cracks in porcelain, improper gap, burned electrodes or heavy carbon deposits.
• Check fuel pump relay. Connect test light between fuel pump test terminal and ground. Turn ignition on. Test light should illuminate for 2 seconds. If test light does not illuminate, check fuel pump relay. For location of fuel pump relay and test connector, see appropriate SYSTEM & COMPONENT TESTING article.
• Check for poor fuel quality or alcohol/water-contaminated fuel.
• Inspect both injector fuses for being open. An open injector fuse causes four injectors and four ignition coils not to operate. Replace the fuse. Inspect the injector circuits and the ignition coil circuits for an intermittent short to ground.
• Check fuel system for incorrect fuel pressure. See BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
• Check for plugged injectors. Perform injector balance test. See FUEL INJECTOR BALANCE TEST under FUEL SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article.
• Check for faulty in-tank fuel pump check valve (if equipped). A faulty check valve allows fuel in lines to drain back to tank after engine is stopped.
• Check EGR operation.
• Ensure Engine Coolant Temperature (ECT) sensor circuit resistance is not too high. See appropriate SENSOR OPERATING RANGE CHARTS article.
• Ensure TP sensor does not stick or bind. A sticking throttle shaft or binding linkage may cause a high TP sensor voltage (open throttle indication). PCM will not control idle if high voltage is sensed.
• Check Idle Air Control (IAC) system. Check for vacuum leak at high idle. Check for binding of throttle blade or linkage. Check for foreign material in IAC bore of throttle body. Check for proper connection of IAC valve electrical connector.
• Check resistance of ECT and Intake Air Temperature (IAT) sensors. On a cold engine, ECT and IAT sensor readings should be within 5°F of each other.
• Ensure correct PCM program is installed in vehicle. Check with dealer for latest application information.
• Inspect the Mass Air Flow (MAF) sensor installation. A MAF sensor that is incorrectly installed may cause a hard start. The embossed arrows on the MAF sensor indicate the direction of the intake air flow. The arrows must point toward the engine. Install the MAF in the proper direction.
• Inspect Crankshaft Position (CKP) sensor clearance and resistance Check harmonic balancer interrupter rings for bent or missing vanes.
• Inspect the Camshaft Position (CMP) sensor for proper mounting and/or a bad connection. A long crank time occurs if the PCM does not receive a CMP signal.
• Check PCM and engine grounds for correct locations, tight and clean connections. See WIRING DIAGRAMS article.