Recurring cat problems

I own a 2000 Honda Civic which I get serviced for regular and scheduled maintenance. It currently has 80,100 miles and I alway use 87 unleaded, never adding fuel or engine “enhancers”, but despite my diligence, I’ve had a run of bad luck with catalytic converters. The dealer replaced the cat in Mar '08 and again in July '08. It’s now Nov '09 and they’ve replaced another cat (luckliy I have not paid out a dime). However, it’s clear that dealer is not getting to the route of the problem as my vehicle is ruining catalytic converters… Any thoughts?

i hate to ask this but the gas your buying. is it major brand or ?major brand gas has more additives to keep fuel system cleaner. all that burnt fuel goes out exhaust.

Catalytic converter failure is most often caused by a problem with the engine and the combustion process. What OBDII codes have accompanied these cat failures? The gas you are buying is not the problem.

major brand gas has more additives to keep fuel system cleaner. all that burnt fuel goes out exhaust.

While it is true that some times major gas brands have more or better additives, it is seldom the cause of the problem reported. Federal regulations mandate a minimum level of additives and few cars need more. In fact most stations even different brand stations get the same gas from the same tanker.

Some brands do sell a supper grade with additional additives but a modern car in good condition should not need them.

That said, major brands are usually under pressure from the brand to make sure they keep their tanks cleaned and filters replaced.

Engine performs OK? Any codes other than P0420?

Only thing I can think of off the beaten path is valve adjustment and get a compression test.

engine has been performing well. I have not noticed any performance issues. P0420 is the only code.
I will ask the dealer to make value adjustments to to run a compression test. I’ve also heard that there might be a software updated to help balance the mixture.

P0420 is the code. Overall the engine seems to be running well.
Other recomendations have been to obtain a software update for the ECU or have the shop make value adjustments or run a compression test.

I am assuming that the dealer has checked the o2 sensors and the fuel injectors. If the engine computer is not messed up then the dealer should be reported to the epa. There is a warranty that applies depending on when you first brought the car in (in miles). Even if they have to replace the entire engine the dealer may be on the hook and perhaps they are stringing you along. They are not “doing you a favor” They MUST fix this BY LAW. Replacing converters is not a way to get out of the epa rules. At 80k miles I believe all systems are under the emissions rule of the epa.

How can I determine if the electronic control unit is good? At this point, I am suspicious that the dealer is not suggesting the ECU as a potential cause of the problem due to EPA emissions warranty.
Would a non-Honda mechanic be able to run a diganosis on a Honda ECU?