Toyota Repair: Catalytic Converter, air fuel mixture, lean mixture

Question
Hi Ted,
I own a 1987 Toyota Corolla,1.6L,4 cyl.Milage:188,000.It suddenly became hard to start.And once I finally got it started it ran poorly and seems to use more gas than usual.I put a new fuel filter on it.I took a look at the spark plugs,which were recently installed and they had a black sooty residue on all of them.I cleaned them and put them back in.The car started up fine but ran poorly.
I let it idle a few minutes and I noticed a spark coming out the tailpipe.I looked under the car and saw that the catalytic converter was beginning to get red.I immediately shut it off.
It seems the catalytic converter is stopped up,so a replacement is in order.
Could that stopped up converter cause the engine to run so poorly?
The car is 18 years old.Does age make a converter fail?
Thank you for assistance.

Answer
The converter is not the cause of the problem, it is only reacting to an engine problem, it may have been destroyed by now from overheating.
There is another problem with the engine, the air/fuel mixture is either too rich or too lean and the computer is trying to compensate for this, there may be an exhaust leak ahead of the converter causing a lean mixture or an engine misfire, you need to check that the engine is operating normally before replacing the converter or you will just burn up another converter because the engine problem is still there, if there is no malfunction with the engine and it is in good condition then the catalityc converter could be clogged up and you need to replace it.