Did a little research on this and some people apparently suggest a new ECU or something...
I hear a lot about "clogged" cats, could this be a possible cause as well? I have no idea how old the cat is.

 

Exhaust leak.

 

Oh okay... that makes sense. I still have a crack in my manifold that needs fixing. I think I'll be taking care of that with headers soon.

Thanks!

 

If you have a crack in the manifold, the o2 sensor is getting bad readings. This will in turn have the ECU crank up the fuel mix. This makes the exhaust sooty which clogs the o2 sensor. The now clogged o2 sensor tells the ECU that things are running even leaner and to crank up the fuel mix. See where we're going here?
Get that manifold fixed ASAP if you are driving it at all. You're sucking down all those carbon monoxide fumes and in the winter it gets worse since you most likely have the windows rolled up.
Once you fix it, clean the o2 with throttle body cleaner (works for me anyway) and reset the ECU. Things should run better then hopefully.

 

could having an exhaust leak cause a engine to burn oil by having the o2 get bad readings thus cranking up the fuel mix??

 

Yes. If the engine is running rich enough, it will wash down the cylinder walls and increase oil consumption since it thins the oil. One good way to tell how bad it is; smell the oil. If it smells gassy, something isn't running right. I think it generally has to be pretty bad to get to that point, but it is noticeable. After fixing an exhaust leak on my '85 4Runner, resetting the ECU and cleaning the o2 sensor the oil consumption was noticeably decreased.

 

Another update:

Got new headers in and the gasket was replaced. My exhaust gives a slight backfire-ish bang after revving at park. Is this something to be attributed to an exhaust leak? Or is it something else?

 

Did you go on to clean the O2 sensors, as Fahrenheit suggested ?

 

what exhaust do you have on their? some mufflers are really good at scavenging ehuast gases and might make your truck backfire... although backfiring is normally an inccorect fuel mixture somewhere along that line....

 

Could be your plug wires. I had the same problem, Mine would "pop" periodically and it turned out to be a bad plug wire.

 

are you still using the air injection? if you are then it may be allowing air to be injected during deceleration, causing any unburnt gas in your exhaust to ignite and make a pop, there should be a valve under the intake that regulates when air is injected or not, a exhaust leak will cause the same thing also

 

94x4:
No, I haven't gotten around to cleaning the O2 sensor. I had planned on doing that after I'd finished the Seafoam treatments. Unfortunately, I can't do that now since the Firehouse is around the corner. I'll probably look into that next weekend.

Jim:
I have a Flowmaster under there. I don't know what kind though.

Yota4runner:
I doubt it'd be my wires. Protrux put in some new Toyota OEM wires just a few weeks ago. I haven't replaced the rotor and cap though. Could that be part of it?

superjoe:
Never heard of it but I'll look into it

Thanks guys I really appreciate all the feedback

 

I was looking into new o2 sensors on my 89 4runner 22re having herd of great improvements in mpg and overall engine performance. Do you think if I simply clean the o2 sensor and reset the ECU it would be as efficient as buying a new one? If so how would I go about cleaning the o2 sensor and resetting the ECU? Any advice you would have would be greatly appreciated. Thanks.