What caused the catalytic converter to get stopped up?

I am looking at buying a 2001 Pontiac Montana with 150,000 miles on it. The dealer said it will be ready tomorrow after he replaces the catalytic converter because the old one was plugged up.


I am wondering what caused the thing to get stopped up? A good friend of mine said that its a bad thing that theres something wrong with the engine.


Should I not buy the car for this reason?


Other than this the car is in great shape with a few minor dings and scratches.|||nothing Wrong with car because they all stop up over time they doing their job to catch particles that pollutes air is why they started adding them al cars have to replace them sometime or another they all stop up|||The only plugged converter I've seen looked like it had black glassy stuff on the inlet side of it. The conventional wisdom is that the glassy stuff is the result of the catalyst matrix melting and what I saw fit that description.





Why that happens is the stuff of debates. Some people say running rich will do it, others point out that running rich doesn't provide the oxygen needed to burn the excess fuel in the converter so it has to be misfire, and still others say retarded timing is to blame.





My take on it is that almost any operating condition (except maybe the timing) that can overheat the converter will set the check engine light anyway. And unless you were talking to the mechanic who actually had his hands on the car I'd expect the real problem to be that the 150K mile old converter was setting the check engine light on a bad catalyst code, and that it was relayed to you as being "plugged purple monkey dishwasher."





I wouldn't be afraid of buying the car.|||converters clog up over time. it just happens. nothing you can really do about it. a lot of mechanics share the same theory i do as far as cat converters go. When you change the oil in your car, there are new chemicals in it that, when burned in your engine, flow into the exhaust and break down the internals of the converter. when that happens, it clogs. there is some serious stuff inside that converter, which is why its so expensive too. nothing is wrong with your engine, and if you want to buy it, knock yourself out. it does seem a little high on mileage, but if you feel its solid, go for it!|||Hi Dale D;


The Cat Converter fails whenever one or both O2 sensors are not working. This causes poor combustion and deposits carbon in the converter. Check the throttle plate for carbon deposits as well. There should be a check engine light on, if not someone may have disabled the light, the vehicle needs service.|||your friend might be right,when a car has that many miles on it the oil rings wear and burn more oil and smokes a little and clogs up the converter,but a converter need to be replaced when you get over 125000 miles because they become ineffective and stop doing their job,hope this helps.|||Make sure you ask the the dealer to prove the replacement converter is a gm replacement.Some aftermarket converters can and will give you problems.Another way to look at it is the factory converter lasted 150,000 miles.|||if the catalytic converter is stopped up. then that is your problem. but if you don't feel that it is good don't buy it.|||carbon.