Initial Inspection and Diagnostic Overview

A visual inspection for loose, disconnected, or improperly routed wires and hoses should be made before attempting to diagnose the fuel injection system. A visual check will help locate these faults and save unnecessary diagnostic time.

1. Check battery cable connections for tightness. The battery should be free of dirt & corrosion. Check color of test indicator on top of battery.
2. Check engine control system ground connections on side of frame rail between battery and air cleaner. They should be free of corrosion.
3. Check engine control system relays connections. Check relays for signs of physical damage and corrosion.
4. Check air cleaner pre-heat hose for rips & tears. Replace damaged hoses. Ensure that the hose is connected to the air cleaner and to the heat stove on the exhaust manifold. Check air cleaner element. If dirty, replace.
5. Check accelerator & cruise control cables for binding. Repair as necessary.
6. Remove the accelerator and cruise control cables. Check operation of the throttle return springs.
a. Remove external throttle spring (attached to the throttle lever and the ISC motor mounting bracket), move the throttle lever to the wide open position and release it. The throttle lever should return immediately to the closed position. If throttle spring on the throttle lever does not operate properly, inspect the throttle spring on the throttle shaft for binding or fatigue. Repair as necessary.
b. Lift the tang of the throttle return spring on the throttle shaft off of the throttle lever to release tension. Connect the external throttle return springs to the throttle lever and ISC motor mounting bracket. Open the throttle to the wide open position and release it. The throttle lever should immediately return to the closed position. If the throttle lever does not operate properly, inspect the throttle return spring for fatigue. Repair as necessary.
7. Inspect the ISC motor connector for damage or corrosion. Inspect the connector wires for scuffing, exposed wire or other damage.
8. Check that the electric cooling fan switch connector is connected to the switch. Inspect for corrosion.
9. Inspect the thermostatic air cleaner (TAC) motor vacuum tube at the thermal vacuum switch (TVS) in the throttle body bonnet and at the air cleaner. Inspect the TVS vacuum supply tube. Replace tubes as necessary.
10. Check the Crankcase Ventilation (CCV) hoses. Replace if damaged.
11. Check the EGR valve solenoid. Ensure that the vacuum tubes are connected to the solenoid and are not damaged. Inspect the wire connector for corrosion.
12. Check coolant temperature sensor for scuffed or exposed wires or corrosion.
13. Check EGR valve and transducer for damage. Check that the back pressure hose is connected to the transducer, that the transducer to EGR valve hose is secure, and that the vacuum supply tube to the transducer is connected. Inspect all vacuum hoses for fatigue or damage.
14. Check the EGR tube for restrictions or leaks.
15. Check oxygen sensor electrical connections for damage or corrosion.
16. Check vacuum brake booster hose for damage and tightness.
17. Check Manifold Absolute Pressure (MAP) sensor vacuum tube for damage. Check connection for corrosion. Check sensor wires for damage.
18. Check harness, connector to connector on dash for damage. Check tightness of mounting bolt.
19. Check speed sensor & connections for damage.
20. Remove throttle body bonnet. Check fuel injector & connectors for damage.
21. Check MAT sensor & connections for damage.
22. Check Throttle Position Sensor & connectors & wiring for damage.
23. Check the body to ground strap connections at the dash panel near coolant bottle & on the cylinder block near the engine oil dipstick for damage & tight connections.
24. Check knock sensor & connector for damage.
25. Verify that distributor cap is attached to distributor, that plug wires are connected to cap & to plugs in correct firing order. Check that coil wire is connected to cap and to coil. Check for corrosion.
26. Check ignition module & coil assembly connections for damage. Check that connectors are completely engaged with module.
27. Check vacuum reservoir & tubes for tightness & damage.
28. Check that the two terminal connectors & output wires are connected to the alternator & check for signs of arcing & corrosion.
29. Check starter connections for corrosion. Check battery cable & solenoid wires for damage.
30. Check fuel guage sending unit & pump electrical connectors for corrosion & damage.Inspect for fuel leaks.
31. Check for collapsed exhaust pipe or muffler.