The Mercedes-benz W201 190e, a classic compact executive car, is known for its robustness and engineering. However, like any vehicle, it can encounter issues. One intriguing problem discussed in online forums involves the vehicle speed sensor (VSS) and its potential impact on engine stalling and restarting, particularly in models equipped with CIS fuel injection systems.
Understanding the mechanism at play is crucial for diagnosing and resolving such issues. In W201 190E models utilizing a road speed sensor, the Engine Control Unit (ECU) uses this input to adjust critical engine parameters. Specifically, the VSS reading influences the electro-hydraulic actuator (EHA) and the air idle control valve. These two components are vital for managing fuel mixture and idle stability.
The theory suggests that a malfunctioning VSS can send incorrect signals to the ECU. If the sensor incorrectly indicates that the car is still moving when it is actually stopping or idling, the ECU might not adjust the air idle control valve in time. This mistimed adjustment can lead to an improper air-fuel mixture at idle, causing the engine to stall.
Furthermore, the issue might extend to difficulty in restarting the engine immediately after stalling. The ECU, still receiving potentially erroneous data from the VSS, could maintain an incorrect setting for the air idle control valve and possibly the EHA. This perpetuated incorrect fuel mixture might prevent the engine from firing up again for a short period, typically one to two minutes, until the system recalibrates or the faulty signal is momentarily disregarded.
Interestingly, some anecdotal evidence suggests that the throttle position switch, when closed at idle, has less influence on this particular system behavior compared to the road speed sensor. This highlights the significant role the VSS plays in managing idle control and fuel delivery in these specific Mercedes-Benz W201 190E models. Addressing VSS issues is therefore paramount in resolving these engine stalling and restart problems.
