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 in the ENGINE PERFORMANCE section. For location of fuel pump test connector, see COMPONENT LOCATIONS in the article SYSTEM/COMPONENT TESTS in this section. Check for blown injector fuse.
- Check for poor quality or water contaminated fuel.
- Ensure TP sensor is not sticking or binding.
- Check EGR operation.
- Check for a leaking injector. To do this on TBI systems, disconnect injector electrical connector at injector. Crank engine and watch for fuel leakage.
- Ensure resistance of coolant sensor circuit or coolant sensor is within specification.
- Check ignition system for a worn distributor shaft, bare or shorted wires, incorrect pick-up coil resistance, loose ignition coil ground or moisture in distributor cap. Check for adequate spark 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 for correct fuel pressure in all speed ranges.
- Check for faulty in-tank fuel pump check valve (MFI only). A faulty in-tank fuel pump check valve will allow fuel in lines 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. Connect a radiator test pump and apply 15 psi (1.0 kg/cm2 ) pressure. If pressure will hold 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 water contaminated fuel, correct fuel pressure or a restricted injector. Check for foreign material in IAC bore of throttle body. Check for proper connection of IAC valve electrical connector. Check for faulty crankcase ventilation valve. Check for failure of A/C compressor or relay.
- Check MAP or MAF sensor. Check for flooding.
- Inspect crankshaft sensor clearance and resistance. Check harmonic balancer interrupter rings for bent or missing vanes.