Experiencing a high idle in your classic 1988 Benz 560sl can be concerning. One potential culprit often overlooked is the throttle position switch. This component, while seemingly simple, plays a critical role in your 560SL’s engine management, particularly at idle. Let’s delve into how the throttle switch can contribute to a high idle issue and how you can diagnose it in your 1988 Mercedes-Benz 560SL.
The throttle position switch on your 1988 560SL is a straightforward switch located on the throttle butterfly shaft. Positioned within the engine’s V, it’s designed to signal the engine control unit (ECU) when the throttle is fully closed (idle) and wide open (full throttle). If this switch fails to register the idle position accurately, it can indeed lead to a persistently high idle in your 1988 Benz 560SL.
Before suspecting the switch itself, it’s wise to first inspect the throttle linkage. Ensure there’s no binding or obstruction preventing the throttle from closing completely against its stop. If the linkage is operating smoothly, the throttle position switch becomes the prime suspect.
Testing the switch on your 1988 560SL is relatively straightforward. Locate the connector on the upper left side of the engine, near the valve cover. This connector, typically with three wires, is connected to the throttle switch. Using an ohmmeter, you can test the switch’s functionality.
To test for the idle position, with the butterfly closed, check for continuity between the common wire and the idle wire at the connector leading to the switch. You should observe continuity. Repeat this test with the butterfly wide open (simulating full throttle), this time checking for continuity between the common wire and the full throttle wire. A lack of continuity in either position indicates a faulty throttle position switch that likely needs replacement to resolve the high idle issue in your 1988 Benz 560SL.
Given its location in a high-heat area of the engine, it’s not uncommon for these switches to degrade over time. Diagnosing and potentially replacing this switch can be a key step in resolving a high idle problem in your 1988 Mercedes-Benz 560SL, ensuring your classic roadster runs smoothly.
