I have deleted my cat, and since my SES light came on for an o2 sensor code (which was expected) but my gas mileage dropped from 200 miles to the tank (in town) to about 140. It's the 3.1l. I was wondering if the rear o2 sensor did anything to control fuel mixture, and if so, can I trick it into giving a correct reading?

 

I'm not really sure if there would be any way to trick it into a correct reading or not but it sounds it me like that may definitely be the problem. The sensors may not be producing the right voltage reading to the ECM because it's getting the same reading as the front O2 sensor and it's telling the ECM that there is to much air in the fuel-air mixture and it's pushing more fuel into the mix to compensate for the loss of the fuel reading.

 

There's only 1 O2 sensor, and it's on the y pipe.. Just replace it and check all the wiring, problem fixed.

 

As said there is no rear O2 sensor and the one in the junction of 'Y' pipe is used by the computer. You need it even if you take the cat off. Taking the cat off shouldn't affect it much if at all.

 

Will do. The light came on as soon as I deleted the cat, it went off but comes on when the car gets really warm occasionally. I also have a surging idle at stops in gear.

 

Need to know which O2S code... Sounds like possibly a 44 to me... And may have a code 33 or 34 as well... Or a 32.

 

Car idled rough today and threw me a code 44. Funny that it waited until I posted to do it . It hasn't thrown a code in probably 3 months now.

 

Check for a vacuum leak first and go from there... Pull a couple or all of the plugs when you get a chance to find out what's going on in each cylinder... Could also be a bad injector or 2.