I've searched all the 'rough idle' threads, but didn't quite find a match for my particular symptoms. Here goes: My idle became rough and slowed to around 600RPM suddenly today at a stop light. This car has always run very smoothly and has been properly maintained(57K miles). I popped the hood and noticed the vacuum hose connected to a valve near the firewall and just to the right rear of valve cover). Only about 1/2" of the vacuum hose had broken off so I simply pulled off the bad piece and reconnected what was left. Pardon my ignorance, but I don't have a manual to ID this valve. I was surprised that the idle did not return to normal after reconnecting this hose, however. Anyone had similar experience? The car is a '93 300SE. It's been a dream to drive so far and still runs great except for the suddenly rough idle.

Thanks,
Ed