I have 1994 C220, with 137K miles. Car runs and idle's good when cold, but as the temperature reaches 80 deg. c on the temp gage or at the steady temp, the engine idle speed surges up and down and one can smell the unburned fuel all over. The process of rough idling continues till the engine dies.

I have changed the plugs, air filter and cleaned plug wires. Also I did change the Over voltage protection relay last year, which solved my earlier prob. of not starting randomly.
Please help me on this.
Thank you and eagerly awaiting reply.