When I park my car, or sometimes when its idling at a stop sign or red light with the window open, I detect a smell similar to burning paraffin comming from the bottom of the car. After sniffing around, it seems like the smell is comming from the exterior of the catalytic converter. The converter appears to have a coating applied to it which looks like it has melted slightly. I know that the converter is supposed to run hot (failure to run hot usually indicates dead catalyst); however, should it run hot enough to melt the coating and should there even be a coating on it? Or is the smell comming from something else?

The smell has been occuring off and on for about 4 years. The converter is the original converter (1987) and appears to be working as the car passed a static emmissions test 18 months ago with no problem.