Engine stalling and failing to restart in your Mercedes-benz W201 190e can be frustrating. While there are numerous potential causes, one often-overlooked culprit could be the Vehicle Speed Sensor (VSS). This article explores how a malfunctioning VSS can lead to these issues in your classic Mercedes.
For W201 190E models equipped with a road speed sensor, the Engine Control Unit (ECU) uses this input to manage engine functions, particularly the idle air control valve and the Electro-Hydraulic Actuator (EHA). The VSS signal informs the ECU about the vehicle’s motion. If the VSS malfunctions and incorrectly signals that the car is still moving when it’s actually stopping, the ECU may not adjust the idle air control valve in time.
This mistimed adjustment can cause the engine to stall as the idle settings are not correctly engaged when the car comes to a halt. Furthermore, the incorrect readings from a faulty VSS can disrupt the fuel mixture settings managed by the ECU, making it difficult to restart the engine immediately. The ECU, still believing the car is in motion, maintains fuel and air settings inappropriate for a stationary engine. This can persist for a minute or two until the system recalibrates or “realizes” the vehicle is no longer moving.
In some cases, pressing the accelerator pedal while starting might help, but until the ECU correctly registers the vehicle speed, starting issues may persist. Interestingly, the throttle position switch, when closed at idle, appears to have less influence on the system’s behavior in this specific scenario than the VSS signal.
If you are experiencing intermittent engine stalling and restart problems in your Mercedes-Benz W201 190E, particularly after slowing down or stopping, investigating the Vehicle Speed Sensor should be a priority. A faulty VSS can disrupt the delicate balance of fuel and air mixture at idle, leading to these inconvenient and potentially dangerous situations.
