the cat has no effect on gas mileage, unless its plugged. the rear 02 only reports on the condition of the cat and does not affect how the engine runs. if your having a problem with tank pressure i would get that figured out. start by fixing the things you know are wrong. when you get stuck, come here or find a shop that you trust.

zedpapa

 

Thanks for all the replies guys im hearing two different sides about the downstream oxygen sensor. I hear that it does affect how your veichle runs without it your jeep woould be stuck in closed loop mode where the jeep is dumping ridocolus amounts of gas in the engine but then some say it doesnt affect anything ?

 

http://www.aa1car.com/library/o2sensor.htm

cat has huge Affect on fuel mileage, and yes the O2 does directly control the air/fuel ratio

 

I have a 88 Cherokee and my o2 sensor was located before my cat so how would that affect it? And I checked my fuel pressure it was low at 28 lbs and my gauge is way off and I just replaced the fuel pump filter injectors and still not fixed

 

88 is not OBD2, so it would only have 1 sensor, my 91 is the same way, I gutted my cat and my power and mileage went up just a smidge

 

What is your actual MPG?

 

11 is the limit on low mileage that is ok by the manufacturer

 

are you talking to me?

I am averaging right now about 16-18mpg, its very windy here lately, so its been rough coming home, uphill and with the wind head on, ive been having to leave it in 4th gear