Originally Posted by Dirty Biker
I noticed the previous owner gutted the cat on the s10 I drive. This is a 1998 s10 with 2.2L, the mileage is horrible. The power is low. It seems to run fine though other than that. Is it possible the downstream o2 sensor is causing me to not stay in closed loop and get bad gas mileage? I have read about others using a non fouler and some steel wool to try to correct throwing the code. Any thoughts? Thanks, Austin
edit: title should read "from downstream o2 SENSOR" instead of CAT" or the like sorry. Thanks
Steel wool? The down stream O2 sensor is comparing what comes out of the cat to the upstream O2 sensor measuring what's going into the cat. This is an issue of the exhaust's chemistry not one of back pressure. The O2s are looking for specific ratios of free oxygen in the exhaust stream and adjusting the mixture accordingly. In this case the computer would be reading excess oxygen which it reads as a lean mixture and is trying to compensate by throwing more fuel in.
I mean like give yourself a break, put the cat back in as it should be, a 2.2L engine isn't being held back by a catalytic converter. The O2 sensor might be toast as well. If you don't live in California you can get an aftermarket converter for a lot less than the OEM part thant will work just fine. Magnaflow and a host of others are the web let your browser do the walking.