Worse gas mileage after changing O2 sensor

[manp0899]

So I got the code for a bad cat. Instead of replacing it I decided to get a URD dummy sensor, where it connects to the downstream sensor and sends a good signal back to the car so I dont get that pesky check engine light disabling my VSC. About a year later and decided that my gas mileage has been sign worse and instead of changing the cat I wanted to replace the O2 sensor for a cheaper solution. After changing the o2 sensor I noticed that my mileage was worse than before. Anyone had a similar situation or solutions that would break the wallet?

 

[Chaz526]

Somebody correct me if I'm wrong, but can't a bad cat cause your MPG to suffer?

 

[gm350reratliff]

Unhook the battery for 30 minutes. Hook the battery back up and let it idle for 30 minutes.

 

[Jeremy556]

So I got the code for a bad cat. Instead of replacing it I decided to get a URD dummy sensor, where it connects to the downstream sensor and sends a good signal back to the car so I dont get that pesky check engine light disabling my VSC. About a year later and decided that my gas mileage has been sign worse and instead of changing the cat I wanted to replace the O2 sensor for a cheaper solution. After changing the o2 sensor I noticed that my mileage was worse than before. Anyone had a similar situation or solutions that would break the wallet?

So, you knew you had a bad cat a long time ago, decided to do a mod to ignore that fact, then when you undid the mod your mileage got worse? Did you do anything to diagnose the problem that caused the clogged cat in the mean time? :ybrick:

 

[earthrealm]

@#3 comment, 10mins is ok both ways..30 mins idle is way too much

 

[manp0899]

So, you knew you had a bad cat a long time ago, decided to do a mod to ignore that fact, then when you undid the mod your mileage got worse? Did you do anything to diagnose the problem that caused the clogged cat in the mean time? :ybrick:

I did not undo the mod. My fear is that the VSC will turn on and in the winter I want to make sure I have my 4wd available. I will most likely try it this spring and see if the Check Engline light turns on then.

I just decided that instead of changing the CAT i try to 02 sensors first. I took the car to the dealership and another mechanic. Other than OBD2 sensor im not sure if they did anything else to diagnose the problem further.

 

[Jakeepoo3]

So I got the code for a bad cat. Instead of replacing it I decided to get a URD dummy sensor, where it connects to the downstream sensor and sends a good signal back to the car so I dont get that pesky check engine light disabling my VSC. About a year later and decided that my gas mileage has been sign worse and instead of changing the cat I wanted to replace the O2 sensor for a cheaper solution. After changing the o2 sensor I noticed that my mileage was worse than before. Anyone had a similar situation or solutions that would break the wallet?

Same thing my cats started going bad right at 100 thousand miles. Truck ran like crap and gas mileage was suffering. Obviously this needed fixed before I could get to removing the exhaust system to get trash can cats out and straight pipe them. I used my existing downstreams and wired in the correct resistor and capacitor to send correct values back to computer. Test with propane torch. Relearned the air fuel ratio. Completely fixed until I get bad cats out. Gas mileage went up almost three mpg.