So heres the problem.

Cracked my exhaust manifold where it bolts to the downpipe Before the O2 sensor. It ran great for a while just had a loud exhaust. Took it on a 950 km road trip (sorry dont know mile conversion) after about 2/3 of the trip my exhaust started backfiring, noticed a decrease in fuel economy. Kept going on in my trip it was fine. Went wheeling for 5 days, no issue except for minor backfiring while cruising down an FSR. Drive home, Truck was fine until i started going downhill, I live in the canadian rockies so these are big hills... Truck would backfire a lot downhill unless i kept my foot on the gas. If i let it backfire for to long it would flood itself out if i hit the gas and die.

My guess here is that the crack in the manifold got worse and is letting to much air in the exhaust before the O2 and my o2 is telling the ecu to dump more fuel in thus causing it to run rich and the excess fuel is thus burning in the exhaust. My question is, can i unplug my o2 sensor until i can get a new manifold or headers or will i still have said issue?

EDIT: Truck is a 22RE with all that ˟˟˟˟ty emissions crap

 

That's exactly what's happening. I had the Y break off my downpipe where it was welded to the exhaust pipe going to the cat. It would drive fine.....loud as hell going down the road, but as soon as you let off the gas it would backfire like a machine gun. fuel mileage was trying to go into the negative too. Fix the exhaust leak and you should be good to go.

I think what's actually happening, rather than letting too much air into the exhaust, you're letting too much exhaust OUT before it gets to the O2 sensor so it's getting a false reading.

 

ya i ordered some headers to clear up teh whole issue in the mean time muffler cement and exhaust tape should hold it together for a little bit. hope that fixes my issue!

 

found the exhaust leak. snapped a stud actually where the manifold meets the head. put some muffler cement on it see if it holds for now until i get the header