Possible Causes

Possible Causes
PCV SYSTEM
IAC MOTOR PASSAGES
VACUUM LEAKS
AIR INDUCTION SYSTEM
THROTTLE BODY AND THROTTLE LINKAGE

1) ACTIVE DTC
Ignition on, engine not running.

With a scan tool, read DTCs.

Is the DTC active at this time?

Yes
1. Go To 2).
No
1. Refer to the INTERMITTENT CONDITION diagnostic procedure.
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
2) PCV SYSTEM
Visually and Physically inspect the PCV system.

Check for the PCV valve disconnected.

Check for an incorrect PCV valve. The PCV valve must meet OEM specifications.

Damage vacuum hose.

Were any of the above condition found?

Yes
1. Repair as necessary.
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
No
1. Go To 3).
3) IAC MOTOR PASSAGES
Turn the ignition off.

Remove the IAC Motor.

Inspect the IAC Motor and passages for any obstructions or damage to motor.

Were any problems found?

Yes
1. Repair as necessary.
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
No
1. Go To 4).
4) VACUUM LEAKS
Start the engine.

Inspect the vehicle for external vacuum leaks.

Inspect the engine for internal vacuum leaks.

Were any vacuum leaks found?

Yes
1. Repair the vacuum leak as necessary.
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
No
1. Go To 5).
5) AIR INDUCTION SYSTEM
Inspect the Air Induction System for the following problems.

Restrictions: Dirty Air Cleaner, Foreign material trapped in the air intake tube, etc.

Leaks: Air Intake tube connection, Air Cleaner housing, etc.

Were any problems found?

Yes
1. Repair or replace as necessary.
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
No
1. Go To 6).
6) THROTTLE BODY AND THROTTLE LINKAGE
Inspect the throttle body plate carbon build up or other restrictions.

Inspect the throttle linkage for binding and smooth operation.

Ensure the throttle plate is resting on the stop at idle.

Were any problems found?

Yes
1. Repair or replace as necessary.
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
No
1. Test Complete.