I disconnected the plastic hose from the EGR on my 96 C280 that runs under the engine cover to the switchover valve this morning. I did that just to see if I could set off a CE light or at least a pending code. I'm dealing with an EGR readiness monitor that is not setting. After a 20 mi drive on street and freeway with accelerations and coastdowns (although not completely to a stop), no CE light or pending code. I will try again on the trip home. Also, I did not notice any change in the way the car drove or idled during the trip. Wondering if this meant anything.

On another occasion, I had connected a vacuum source to this EGR plug when the engine was idling. It stumbled for a few seconds when applying vacuum but then returned to a normal idle even though the vacuum was still applied. Should the idle have stayed rough until the vacuum was released?

Thanks.