Initial Inspection and Diagnostic Overview

A visual inspection for loose, disconnected or incorrectly routed wires and hoses should be made. This should be done before attempting to diagnose or service the fuel injection system. A visual check will help spot these faults and save unnecessary test and diagnostic time. A thorough visual inspection will include the following checks:

Powertrain Control Module(PCM):

1. Verify three 32-way electrical connectors are fully inserted into connector of Powertrain Control Module (PCM).
2. Inspect battery cable connections. Be sure they are clean and tight.

Power Distribution Center(PDC):

3. Inspect fuel pump relay and air conditioning compressor clutch relay (if equipped). Inspect ASD relay connections. Inspect starter motor relay connections. Inspect relays for signs of physical damage and corrosion. The relays are located in Power Distribution Center (PDC). Refer to label on PDC cover for relay location.

Ignition Coil:

4. Inspect ignition coil connections. Verify coil secondary cable is firmly connected to coil.
5. Verify distributor cap is correctly attached to distributor. Be sure spark plug cables are firmly connected to the distributor cap and the spark plugs are in their correct firing order. Be sure coil cable is firmly connected to distributor cap and coil. Be sure camshaft position sensor wire connector (at the distributor) is firmly connected to harness connector. Inspect spark plug condition. Refer to Ignition. Connect vehicle to an oscilloscope and inspect spark events for fouled or damaged spark plugs or cables.
6. Verify generator output wire, generator connector and ground wire are firmly connected to generator.
7. Inspect system body grounds for loose or dirty connections. Refer to Wiring for ground locations.

PCV Valve Hose Connections:

8. Verify positive crankcase ventilation (PCV) valve operation. Refer to Emission Control System for additional information. Verify PCV valve hose is firmly connected to PCV valve and manifold.
9. Inspect fuel tube quick-connect fitting-to-fuel rail connections.
10. Verify hose connections to all ports of vacuum fittings on intake manifold are tight and not leaking.
11. Inspect accelerator cable, transmission throttle cable (if equipped) and cruise control cable connections (if equipped). Check their connections to throttle arm of throttle body for any binding or restrictions.
12. If equipped with vacuum brake booster, verify vacuum booster hose is firmly connected to fitting on intake manifold. Also check connection to brake vacuum booster.
13. Inspect air cleaner inlet and air cleaner element for dirt or restrictions.
14. Inspect radiator grille area, radiator fins and air conditioning condenser for restrictions.

Intake Manifold Air Temperature Sensor - Typical:

15. Verify intake manifold air temperature sensor wire connector is firmly connected to harness connector.

Sensor And IAC Motor Location-Typical:

Rubber L-shaped Fitting - MAP Sensor-to-Throttle Body:

16. Verify MAP sensor electrical connector is firmly connected to MAP sensor. Also verify rubber L-shaped fitting from MAP sensor to throttle body is firmly connected.
17. Verify fuel injector wire harness connectors are firmly connected to injectors in correct order. Each harness connector is numerically tagged with injector number (INJ 1, INJ 2 etc.) of its corresponding fuel injector and cylinder number.
18. Verify harness connectors are firmly connected to idle air control (IAC) motor, throttle position sensor (TPS) and manifold absolute pressure (MAP) sensor.

Engine Coolant Temperature Sensor:

19. Verify wire harness connector is firmly connected to engine coolant temperature sensor.
20. Raise and support vehicle.

Upstream Oxygen Sensor:

Downstream Oxygen Sensor:

21. Verify both upstream and downstream oxygen sensor wire connectors are firmly connected to sensors. Inspect sensors and connectors for damage.
22. Inspect for pinched or leaking fuel tubes. Inspect for pinched, cracked or leaking fuel hoses.
23. Inspect for exhaust system restrictions such as pinched exhaust pipes, collapsed muffler or plugged catalytic convertor.
24. If equipped with automatic transmission, verify electrical harness is firmly connected to park/neutral switch.
25. Verify electrical harness is firmly connected to rear wheel speed sensor. Verify rear wheel speed sensor is firmly attached to rear axle with proper air gap.
26. If equipped with 4-wheel antilock brake system, verify electrical harness is firmly connected to each front wheel speed sensor. Verify both front wheel speed sensors are firmly attached.
27. Verify fuel pump/gauge sender unit wire connector is firmly connected to harness connector.
28. Inspect fuel hoses at fuel pump/gauge sender unit for cracks or leaks.
29. Inspect transmission torque convertor housing (automatic transmission) or clutch housing (manual transmission) for damage to timing ring on drive plate/flywheel.
30. Verify battery cable and solenoid feed wire connections to starter solenoid are tight and clean. Inspect for chaffed wires or wires rubbing against other components.