The Mercedes-Benz W201 190e, a classic admired for its engineering, can sometimes present perplexing issues like engine stalling and difficulty restarting. One often overlooked culprit in this scenario is the Vehicle Speed Sensor (VSS). While it might seem unrelated to engine function, in systems like the CIS-E injection used in many 190E models, the VSS plays a crucial role in idle control and overall engine management.
To understand this connection, it’s essential to grasp how the CIS-E (Continuous Injection System – Electronic) fuel injection system and the Engine Control Unit (ECU) interact in your benz w201 190e. The ECU doesn’t operate in isolation; it relies on a network of sensors to make real-time adjustments for optimal engine performance. Among these sensors, the VSS informs the ECU about the vehicle’s speed, a parameter that influences various engine functions, particularly idle control.
The ECU utilizes inputs from sensors like the VSS to manage actuators such as the Electro-Hydraulic Actuator (EHA) and the air idle control valve. These components are vital for maintaining a stable idle and ensuring smooth transitions between different driving conditions. When the VSS signals that the vehicle is still in motion, even when decelerating or coming to a stop, the ECU might not activate the air idle control valve promptly. This mistiming can lead to insufficient air intake at idle, causing the engine of your benz w201 190e to stall.
Furthermore, a faulty VSS can disrupt the delicate balance of the fuel mixture. The ECU, receiving incorrect speed data, might miscalculate the fuel requirements for idle, leading to a “cocked up” fuel mixture – a term that aptly describes the resulting imbalance. This improper mixture can not only cause stalling but also hinder restarting the engine immediately. The engine may struggle to fire up for a minute or two until the system potentially recalibrates or the faulty VSS signal is momentarily ignored.
Interestingly, the throttle position switch, which also provides idle-related input to the ECU, appears to have less influence in overriding a faulty VSS signal in these specific stalling scenarios. This suggests the VSS signal holds significant weight in the ECU’s idle control strategy for the benz w201 190e.
For owners of a benz w201 190e experiencing intermittent engine stalling and restart issues, especially after deceleration, investigating the Vehicle Speed Sensor is a worthwhile diagnostic step. While other factors can contribute to stalling, understanding the VSS’s role in the CIS-E system can guide you towards a more accurate diagnosis and effective repair, ensuring your classic Mercedes continues to run smoothly.
