Originally Posted by Oldblue

Don’t change the messenger (O2 sensor) it’s doing it’s job, telling you there’s a problem, the catalytic converter is fouled.

Originally Posted by RetroHHR2020

thanks for the links to other posts - as this car was already at 169K when i bought it i don't know the history. Right away i had to replace the lower arms due to shot bushings before i could get it aligned. ran a can of seafoam thru the gas tank and drove across florida back and forth - about 160 miles each way. on the way back a few weeks ago, car was running pretty crappy until i had been driving on the freeway for about 15-30 min... had the scanner monitoring the RPMs the whole way... After that first 30min on the way home, the car ran smooth as can be for a 4banger. since then a few hundred miles of mostly around tampa bay area - lots of stop and go. Never has been as bad since, so thinking the injectors were prob a little dirty too.
When i do an oil change soon I'm going to check and clean the connections on the O2 sensors.

Oh, and on another forum where certain cars have issues with the cats after 20 years, i read someone who recommended removing the upline o2 sensor and spraying the seafoam spray version up in there ahead of the cats and then taking a robust highway drive to 'clean' out the cats. Not sure that's a smart idea or effective.