Idle speed control valve. Porsche 928S4 5.0L 1987-92 / 928GT 5.0L 1989-91  ❭  92860616100

The Idle Speed Control Valve product reference 92860616100  (also called an idle air control valve or IACV) is a precision engine management component designed to regulate engine idle speed by controlling the amount of air allowed into the intake system when the throttle is closed. On early Porsche 928 models this part plays a critical role in stabilising idle, especially during cold starts, changes in electrical load (A/C on, lights on), and during deceleration.

Fits:
Porsche 928S4 5.0L 1987-92

Porsche 928GT 5.0L 1989-91

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Diagram ref no 12

Why This Should Be Replaced Over time, the idle speed control valve can become clogged with carbon, varnish, and oil residues from the intake system. This contamination inhibits the valve’s ability to move freely, leading to poor control of idle air flow. Replacing the valve restores proper engine management and smooth idle operation. 

Replacement is recommended when: The idle speed control valve becomes sluggish, sticks, or fails completely. The engine struggles to maintain a stable idle under varying loads. The valve has exceeded typical service life due to age, mileage, or contamination. Continued operation with a failing idle valve can lead to rough engine operation and increased stress on other engine systems.

Common Issues / Symptoms of Failure

A faulty or worn idle speed control valve often causes a variety of drivability issues:

• Unstable idle: Engine RPM fluctuates up and down at idle. 
• High idle: Engine runs faster than normal when warm. 
• Low idle / stalling: Engine may stall unexpectedly when coming to a stop or when loads change (e.g., A/C switched on). 
• Hard starting: Especially noticeable during cold starts. 
• Hesitation or rough running: When the system fails to adjust air flow correctly. 
• Check Engine Light: ECU may set idle-related fault codes if the idle valve isn’t responding. 

Related reference numbers
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92860616100

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