Tony,
Chicken... Egg... Chicken ... Egg ...
Which came first?
You're assuming that, in your case, that the cat codes caused the poor fuel economy.
More likely, the conditions that caused the poor fuel economy, ie, misfire, lazy upstream O2 sensor, or whatever caused an excessively rich exhaust, caused the cat to fail due to all the unburned fuel that was dumped into it. This then set the efficiency codes..
Makes more sense...doesn't it?
My 98 had recurring problems with the HO2S11 (P1131) several times, then misfires before 75K miles. Sure as can be, it got new cats under warranty as I've previously reported.
It is my conclusion that, in my case, the cat failure was accelerated by the rich conditions (P1131) and the unburned fuel from misfires.
hotrod,
I discussed MIL eliminators in detail a couple of months ago. See if you can dig up that tread in this forum.
Steve
