What could foul both front catalytic converters?
Just my luck. I went to get smog checked, and during the test my check engine light came on, causing me to fail, in spite of having clean emissions.
The code generated was P0420, indicating problems with either the rear O2 sensor or the catalytic converter.
I took my '02 Cherokee to my mechanic and he says that both front cats are bad and need replacing for $600. (honestly, I didn't know I had more than one, but he tells me that there are three: two in front, and one in back).
What can cause both front cats to go simultaneously? The jeep runs perfectly, and I get 21 mpg on flat highways, and my emissions were really clean. I currently have 164,000 miles on it. I don't seem to be losing any significant engine oil.
I always buy 89 octane gas, but I buy it from whatever station sells it cheapest. Half the time it'll be a big brandname, and otherwise it will be an independent.
One time I added a bottle of Risalone oil treatment about 20k miles ago.
About every other oil change I add a bottle of gas treatment to the tank to clean the fuel injectors.
Last year the engine computer went out, and before I replaced the thing, it would run a bit rough, and sometimes blow blue smoke out the exhaust if I accelerated hard.
Does anyone see any red flags in what I've mentioned that would cause both cats to go bad?