Bad CAT, and I can't decide what to do...

[rh77]

OK, so the CEL has been coming on and off for a year or so now on the TL -- "Bad Catalyst Efficiency". I confirmed today that the catalytic converter is indeed not working as it should (the 02 sensor after the CAT varies in voltage in tandem with the upstream sensor, indicating that the converter isn't doing it's job. The downstream sensor should be relatively flat in voltage).

So, here lies the dilemma. The system is forcing the engine to run rich, because it thinks the post-cat emissions contain too little oxygen, but it's just that the CAT's bad. With 126K miles on the odo, and not knowing how long we're keeping the car, I can't decide what to do.

A CAT costs a lot to buy and install, but will reduce emissions and is better for the environment.

If I trick the downstream sensor signal into a flat voltage that's considered richer, the car will rely on the pre-cat sensor and other factors to alter the fuel trim. Right now, it's running rich at +1-1.25 trim, which kills mileage, and I think it's seeing that the post-cat readings aren't right.

We don't have emissions testing, so it won't be tested and require repair, but I guess I know that it's bad. What to do???

RH77