Idle speed smooth running control, display evaluation
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 1999 Volkswagen Jetta, 1998 Volkswagen Jetta, 1997 Volkswagen Passat, 1997 Volkswagen Jetta, and 1996 Volkswagen Passat. However, it is still accessible from the selected car via links, so may be relevant.
- The injection system is equipped with an idle speed smooth running control. There may be power differences between the individual cylinders (component tolerances, jet drillings, compression, etc.) that are recognized and equalized by means of selective injection quantities.
- Recognition at idle speed is via the signal from the engine speed sensor, which delivers four signals per crankshaft revolution to the Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM). If the signals are delivered at the same rhythm, then all cylinders operate the same way. If one cylinder is weaker, then the crankshaft takes longer for the next half revolution. Conversely, a more powerful cylinder accelerates the crankshaft in less time.
- If the Diesel DFI ECM recognizes a time difference, then the relevant cylinder is given more or less fuel, until the engine runs evenly again.
- The measuring value block displays the injected quantity differences of the individual cylinders compared with cylinder Cyl. 3, which is required to ensure an even engine idling speed.
- + mg/H values: The relevant cylinder is less powerful than Cyl. 3 and is therefore supplied with more fuel.
- - mg/H values: The relevant cylinder is more powerful than Cyl. 3 and is therefore supplied with less fuel.