Engine - Idle Speed Hunts When Cold

Group: 24
Number: 93-06
Date: November 15, 1993

Subject:
Idle Hunting

Model(s): Golf, Jetta, Fox, Cabriolet, Corrado, Vanagon, Passat
from 1988 m.y.

All vehicles with Digifant I and II

Condition

After initial cold starts, the idle speed hunts for approximately one minute. After this period, the idle speed returns to normal.

Explanation

Idle hunting is an indication of a properly functioning idle air control system trying to compensate for varying fuel/air mixtures.

Proper fuel/air mixture is required at all phases of operation. Idle hunting is in many cases caused by improper fuel mixture during the initial start-up phase. The Idle Air Control (IAC) Valve attempts to compensate for a low RPM by opening wider, increasing the air flow and in turn increasing the fuel injection time. When the mixture burns completely, the RPM will increase and the IAC will close. Idle hunting is due to the rapid opening and closing of the valve.

Replacing the Idle Air Control (IAC) Valve will not resolve this condition. To ensure proper diagnosis and replacement of the IAC valve, you must get prior repair authorization from your Warranty Adjuster or your DSM.

Service

- First verify that the IAC system functions properly by checking the idle stabilization system, see Repair Manual, Repair Group 24.

- Check fuel injectors and intake valves for carbon deposits. If necessary perform cleaning procedure as described in brochure: "Solving Driveability Complaints", No. WSP 521 154 00.

- Perform diagnostic and troubleshooting procedure as described in brochure: "Solving Driveability Complaints"