Chrysler Repair: EGR valve/O2 sensor: burning up, chrysler cirrus, 1999 chrysler cirrus

Question
Hi Kevin,
I have a 1999 chrysler cirrus 2.5 with approx. 44,000 miles. I had a check engine light come on 10/09 which coded a bad 02 sensor. I had that replaced (the more expensive out of all that are on the car--$250.00). Three months later it just turned over--no start. The shop installed a used distributor along with a new rotor & cap. Three months ago the EGR valve burned up and I installed a new one. Last wee I heard a hissing noise and found the EGR valve to be bad again. This time I replaced that and gave it a complete tune-up. I'm at a loss with this and hoping you can help with a proper direction as to why these are going bad. I get the feeling I'm missing the root cause of the problem and these parts will continue going bad unless whatever it is--is corrected. I've talked to a couple of mechanics re: this and I'm getting different views/opinions.

Answer
Hi John,
The distributor is probably unrelated to the O2 sensor/egr issue. My suspicion is that the catalytic converter has a loose honeycomp and so the exhaust gas is being bottled up partially in the exhaust system which puts a heat strain on the egr and the sensor. You can have a muffler shop test the flow through to see if it is impeded or look for some other obstruction in the exhaust pathway. Absent a code of some sort I can't think of anything else that would do damage to those two exhaust system parts. The catalytic converters do have a finite life and one way the fail is that the honeycomb through which the gases have to pass to have the catalytic process occur come loose, rattle around (which you may hear), and shift off axis so the gases cannont get through efficiently.
Please let me know if I am correct or not. I will try to think of another reason why this would happen without a fault code.
Roland
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Sorry for the delay in responding but I just found the question in the 'pool' to which Kevin had referred it.