Diagnostic Aids

Perform this test only when directed by CIRCUIT TEST AC, step 11). This test is intended to diagnose:

• IAC system.
• EGR system.

To prevent replacing good components, be aware the following non-EEC-IV areas may be at fault:

• Faulty power or ground connections.
• Secondary ignition (wires, coil pack and plugs).
• Engine mechanical components (compression, timing, valves, etc.).

1) IAC Check  Try to start engine at part throttle. If engine starts and runs smoothly at part throttle, go to CIRCUIT TEST KE, step 4). If engine does not run as described, go to step 3). If engine starts and idles smoothly, go to step 2).

2) Check For RPM Drop  Turn ignition off. Connect a tachometer to engine. Start engine. Disconnect IAC solenoid. If RPM drops or engine stalls, reconnect IAC solenoid and go to step 3). If RPM does not drop, go to CIRCUIT TEST KE, step 4).

3) Check EGR Vacuum  Disconnect and plug vacuum line at EGR valve. Attempt to start engine. If vehicle did not start previously but starts now, or if driveability symptoms are eliminated, go to CIRCUIT TEST DL, step 15). If vehicle could not start previously and still does not start, or if vehicle driveability fault is still present, go to step 4).

4) Check EGR Valve  Inspect EGR valve for leaks. If valve is fully closed, go to CIRCUIT TEST H. If EGR valve is leaking or is not fully seated, repair or replace valve as necessary.