Possible Cause & Correction
Check the following items:
- Check fuel pump relay by connecting test light between fuel pump relay connector ignition feed circuit and ground. Turn ignition on. Light should illuminate for 2 seconds. If light does not illuminate for 2 seconds, see FUEL PUMP RELAY under FUEL SYSTEM in SYSTEM/COMPONENT TESTS article. For location of fuel pump test connector, see COMPONENT LOCATIONS in SYSTEM/COMPONENT TESTS article. Check for blown injector fuse.
- Check for poor quality or water contaminated fuel.
- Visually inspect injector fuse(s).
- Check for a binding or sticking TP sensor, or high TP sensor voltage with throttle closed.
- Check EGR operation.
- Check for a leaking injector.
- Ensure resistance of engine coolant sensor circuit or engine coolant sensor is within specification. See SENSOR RANGE CHARTS article.
- Check for proper spark output using Spark Tester (ST-125).
- Check for shorts by spraying plug wires with a fine mist of water.
- Remove spark plugs and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits.
- Check fuel pressure.
- Check for loose ignition coil ground. Also check ignition coil fuse.
- Check for faulty in-tank fuel pump check valve (if equipped). A faulty in-tank fuel pump check valve will allow fuel to drain back to tank after engine is stopped. To check this condition, turn ignition off, disconnect fuel pressure line at fuel rail and remove filler cap. Using a radiator test pump, apply 15 psi (1.0 kg/cm2 ) pressure. If pressure holds for 60 seconds, check valve is okay.
- Ensure the installed PROM is correct for that particular vehicle. Check with dealer for latest application information.
- Check for restricted exhaust system.
- 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 for failure of A/C compressor or relay.
- Check MAP or MAF sensor.
- Inspect crankshaft sensor clearance and resistance. Check harmonic balancer interrupter rings for bent or missing vanes.
- Check if crankcase ventilation valve is stuck open.
- Check basic engine mechanical problems (i.e. compression, valves).
- Check distributor vent system (if equipped).