Preliminary Checks

Most driveability problems in the throttle body fuel injection system result from faulty wiring and/or leaking vacuum hoses and hose connections. To avoid unnecessary component testing, visual check should be performed before beginning trouble shooting procedures. A preliminary visual check should include:

• Air ducts at air cleaner and throttle body.
• Air cleaner pre-heater hose.
• Air filter element.
• All electrical connections at components.
• Throttle return springs.

Check vacuum lines for tight leak-free connections in these areas:

• Throttle body.
• Charcoal canister.
• PCV valve to intake manifold vacuum port.
• EGR solenoid.
• MAP sensor.

Ensure the following electrical connectors are properly attached:

• Battery connections.
• EGR solenoid.
• Engine control system ground connections on side of frame rail between battery and air cleaner.
• Engine control system relays connections.
• Idle Speed Control (ISC) motor.
• MAP sensor connector.
• Speed sensor connector.
• Throttle body temperature sensor connector.
• Radiator fan relay connector.
• TPS connector.
• Fuel injector connector.
• Oxygen sensor connector.
• Coolant temperature sensor connector.
• Distributor connector.