FUEL INJECTION TROUBLESHOOTING
| NOTE: | This is GENERAL information. This article is not intended to be specific to any unique situation or individual vehicle configuration. The purpose of this Troubleshooting information is to provide a list of common causes to problem symptoms. For model-specific Troubleshooting, refer to SUBJECT, DIAGNOSTIC, or TESTING articles available in the section(s) you are accessing. |
BASIC FUEL INJECTION TROUBLESHOOTING CHART
| CONDITION & POSSIBLE CAUSE | CORRECTION | |
|---|---|---|
| Engine Won't Start (Cranks Normally) | ||
| Cold start valve inoperative | Test valve and circuit | |
| Poor connection;vacuum or wiring | Check vacuum and electrical connections | |
| Contaminated fuel | Test fuel for water or alcohol | |
| Defective fuel pump relay or circuit | Test relay and wiring | |
| Battery too low | Charge and test battery | |
| Low fuel pressure | Test pressure regulator and fuel pump, check for restricted lines and filters | |
| No distributor reference pulses | Repair ignition system as necessary | |
| Open coolant temperature sensor circuit | Test sensor and wiring | |
| Shorted W.O.T. switch in T.P.S. | Disconnect W.O.T. switch, engine should start | |
| Defective ECM | Replace ECM | |
| Fuel tank residual pressure valve leaks | Test for fuel pressure drop after shut down | |
| Hard Starting | ||
| Disconnected hot air tube to air cleaner | Reconnect tube and test control valve | |
| Defective Idle Air Control (IAC) valve | Test valve operation and circuit | |
| Shorted, open or misadjusted T.P.S. | Test and adjust or replace T.P.S. | |
| EGR valve open | Test EGR valve and control circuit | |
| Poor Oxygen sensor signal | Test for shorted or circuit | |
| Incorrect mixture from PCV system | Test PCV for flow, check sealing of oil filter cap | |
| Poor High Speed Operation | ||
| Low fuel pump volume | Faulty pump or restricted fuel lines or filters | |
| Poor MAP sensor signal | Test MAP sensor, vacuum hose and wiring | |
| Poor Oxygen sensor signal | Test for shorted or open sensor or circuit | |
| Open coolant temperature sensor circuit | Test sensor and wiring | |
| Faulty ignition operation | Check wires for cracks or poor con- nections, test secondary voltage with oscilloscope | |
| Contaminated fuel | Test fuel for water or alcohol | |
| Intermittent ECM ground | Test ECM ground connection for resistance | |
| Restricted air cleaner | Replace air cleaner | |
| Restricted exhaust system | Test for exhaust manifold back pressure | |
| Poor MAF sensor signal | Check leakage between sensor and manifold | |
| Poor VSS signal | If tester for ALCL hook-up is available check that VSS reading matches speedometer | |
| Ping or Knock on Acceleration | ||
| Poor Knock sensor signal | Test for shorted or open sensor or circuit | |
| Poor Baro sensor signal | Test for shorted or open sensor or circuit | |
| Improper ignition timing | See VEHICLE EMISSION CONTROL LABEL (where applicable) | |
| Check for engine overheating problems | Low coolant, loose belts or electric cooling fan inoperative | |
| NOTE: | For additional electronic fuel injection trouble shooting information, see the appropriate article in the ENGINE PERFORMANCE section (not all vehicles have Computer Engine Control articles). Information is provided there for diagnosing fuel system problems on vehicles with electronic fuel injection. |
