Well I thought I had the problem fixed(yall are gonna be pissed, i put back on the hollowed out cat) but aparrently not, my truck is getting terrible mileage even after I ran 93 octane with injector cleaner and octane booster in it. It seemed to get better mileage untill i developed an exhaust leak where I welded the cat back onto the truck. The downstream o2 sensor on the exit side of the cat isnt hooked up so could that be the problem? The upstream sensor is fine but the wires got cut on the second one. If this is indeed the problem I think I am going to go get duals with dual flows coming out under the bed. Does that seem like a good setup, and how much will it cost? I really need some help because this gas is too expensive to be wasting. The Truck seems to run fine but that gas needle drops pretty quick. Could the exhaust leak be my problem? All help is appreciated, but flames arent.

 

The 2nd O2 sensor just verifies that the Cat is working properly. You should have a CEL if it's not hooked up. The crappy fuel economy can be caused by several things. First thing is the upstream O2 sensor. They do go bad, and when they do the truck will tend to run poorly. You could also have fuel supply issues such as a stuck injector.

 

bump

 

If the 2nd o2 is not hooked up the computer may be thinking the truck is running bad and putting more fuel too it, thus causing it to run rich and hurting fuel mileage.

 

you also should have an engine light on, if you do pull the code
Se7eN

 

I noticed today that when the truck was idling it was smoking and the idle was pretty erratic like it was loading up. Is it running too rich? Think that the upstream 02 sensor is bad? I removed it and it dosent look too bad. Where can I get a good 02 sensor that's not like 80 bucks?