Catalytic converter

I have a 1997 Mercury Grand Marquis with 88,000 miles, almost perfect. For most of those miles it was normal driving, but for the last 3000 or so, mostly in-town very short trips. I got the 90,000 mile service (the check engine light had come on). They said the right catalytic converter is bad. One, will it hurt the car to not replace this? Two, is this a normal age for this occurrence? Three, is the intensive short trip use a likely culprit?

I would replace it. Chances are this is the only time you will need to do so. You may want to get a second opinion and estimate of cost. If your first estimate is from the dealer, you are likely to find the second one will be a lot less using an after market part. I suspect all those short trips contributed to it.

I am assuming the original diagnoses was correct, but it is possible to confuse a problem with a sensor or a converter.

Not replacing it will likely result in lower mileage and power as time goes on.

Note: hellokit and I are both trying to say the same thing. You do need a second opinion for the reasons kit stated. I fear my original message was too weak in the way I stated it.

I’m not assuming a diagnosis was done. Pulling the trouble code and declaring the catalytic converter kaput is not diagnosis!
Go to an independent shop and ask that a real diagnosis be performed. This would involve (partly) checking the operation of the oxygen sensors. Bad oxygen sensors can erroneously indicate a bad catalytic converter.
Short trips do involve more cold engine operation where the engine operates at less than optimum. Change the spark plugs to help the engine run its best.
When you find a good mechanic/shop, s/he can advise you on other routine maintenance to perform.

Many people get 200,000 miles with out a cat.failure. We get many posts regarding 02 sensor, cat.failure diagnosis and replacement with many people having continous problems in these areas.

My opinion is that many mechanics are not competent in these areas (driveability and emissions) and mistakes are being made.

Have the shop explain how they came to the conclusion about your cat. Cats. can be checked with a vacuum gague for restriction,cats can be checked for their ability to convert CO and HC into CO2 and water. There are three seperate tests to do this,first is a temperature test there should be a increase of at least 100F between inlet and outlet,the next test requires a gas analyzer that can check the cats. ability to store oxygen,finally you can check the cats. efficiency with a four or five gas analyzer,you check the CO2 readings on a car with a heated up cat. but with the ignition disabled and the engine being cranked.

I say no on the short trip root failure cause idea. I have replaced more for rattling than efficiency. Cats. need a correctly functioning fuel control system to function correctly,they need to cycle between rich and lean.

They should at least do the temp test before calling your cat. bad. and to prevent a repeate failure a root cause must be determined and a confirmation of correct fuel control system operation must be made after repair.

Or you could just wing it,put a new cat.on,clear the codes and send you down the road.

A failed 02 sensor will store a DTC for the sensor (but make sure its the sensor),the computer uses the data from the sensor to run the diagnostic monitor for the cat and the EGR. Once the 02 code is set cat. and EGR monitoring is suspended. Once the 02 is repaired it is possible for another code to set because the 02 code was blocking the other areas.