Rough Idle, 0420 Code - So Many Trips to the Mechanics and No Resolution. Toyota Corolla.
So, I have a Corolla [about 90,000 miles] that idles rough (rougher when I use the power windows or the AC) and is throwing a 0420 code. Here's what's happened up to this point:
1) First, for years it ran fine and I didn't have a single problem with it. Then it started accelerating sludgily, using gas faster than normal, idling roughly and the 0420 code came up.
2) I took it to my [trusted] mechanic [Mechanic 1]. They referred me to a shop that specializes in catalytic converters [Mechanic 2] and the like for the 0420 code and referred me the dealership for the idle problem. He said that the dealership has more experience with my specific car.
3) I have gone back and forth between the dealership and Mechanic 2 about ten times total. They cannot seem to figure the thing out.
4) The dealership replaced the air fuel sensor and a seal on the mass air flow sensor. [I got sleazy vibes from these guys.]
5) Mechanic 2 replaced the catalytic convertor (and is about to replace it again -- something about a hole in the replacement), both O2 sensors, the spark plugs and ran some kind of cleaners through the fuel system. They seem to be running all kinds of tests, doing research (I sat at the shop, for part of a day, and watched as a mechanic moved back and forth between my car, some devices and a computer, in an increasingly harried manner) and working with someone outside of the shop called the "tech team." [I've gotten good vibes from these guys.]
6) I've cleaned the mass air flow sensor with electronics cleaner, replaced the engine filter and also replaced the battery (it was close to dying).
7) I've dropped $1,800+ on these problems (which is a lot for me).
8) The sludgy acceleration has mostly gone away, but the other two issues are still present. I'm worried that this next fix, re-replacing the catalytic converter, won't work either. (I wouldn't be paying for the re-replacement, but I'm worried about the car.) Mechanic 2 said I'd be able to pick up my car today (it's been in the shop for four days). Also, both my Mechanic 1 and 2 said that, although troubled, my car is okay to drive.
What do I do? [I've begun to fixate.]