how do you know whether to replace your catalytic converter? can a bad converter cause poor gas mileage but not affect the performance much? truck has 135k miles and its the original cat.

thanks

 

I don't know the answer to your question with the cat. However, I have read that O2 Sensors that aren't OBDII compliant are sugested to be replaced approximately every 30,000 miles. I have a 95 dodge ram looking to replace my O2 sensors. I have 75,000 miles on the orginal O2 sensor. If I understood the article correctly, sut can build up around the inlet to the O2 sensor not allowing it to read the actual amount of O2 in you exhaust. This will cause the computer to think your not running 14:1 and will compensate for it. Hence, because the inlet maybe partially close to the O2 sensor, the computer will lean out the mixture to see the right mixture at the O2 sensor. This maybe why you are not seeing the performance you once had. I am not any expert. I will be changing out my O2 in the very near future to see if that helps my performance.

 

i replaced both oxygen sensors just about 8000 miles ago. that didn't seem to affect anything. truck ran the same as before. performance is still great but the mileage isn't. i know the rams don't get great mileage, but it doesn't matter whether i drive it all highway, all city, lead foot or granny style, the mileage is always right at 12 mpg. i would think it would at least increase a little in highway driving.