I recently switched back to 3.73's from 4.62's and i have actually been paying attention to the gas mileage now. It probably has not changed much from the axel swap  but i'm only getting around 12mpg. 31's and a 4-1 case. It has a 1.6 8v swap from an obd 1 tracker, header and big exhaust. The oxegen sensor is bent at the wire end from the engine leaning on it before it was put in. Also when i wired the generic style sensor to a stock plug i had two reds and a black on the plug and two whites and a black coming out of the sensor. Does it matter which red goes to which white?

How are you calculating your MPG? Have you re-calibrated your odometer for the larger tires? With 31" and t-case gears, I would think you should be getting much closer to 20MPG. Maybe a little more if it's fuel injected.

The speedo is dead on with the case and 31's. I found one of the little radar trailors the cops put out and cruised by it a few times to check.  I never calculated it with the 4.62's . I would be thrilled with 20 at the moment

 have you pulled the codes ?

There's got to be something going on. I know the ECU will go into a "limp home" mode and run intentionally too rich (as it's less destructive than too lean) if it's throwing a code. Get that thing scanned.

 yep my bet is she is throwing a code  your MPG is just to low .
 my bet is that for some reason your ECM has went to limp home/ fail safe mode

 I agree that it is running in closed loop mode. It is obd1 so i flashed it and i only got the 12 code which is normal. I'm just curious if the sensor is bad but not showing a code. The egr system may not be working due to the hole inthe thorley header not lining up compleatly over the hole in the block  causing a little exhaust leak but i was told that it wouldn't cause a noticable difference. Thanks for the help so far fellas

 Buy  chance you have not taken the battery cables off  since you last  drove it for 30 minutes or so did you ?
 if so it cleared the ECM and all you will get is a code 12  tell more info is logged .
 you need a OBD scan.  take it to a dealer or local shop that can do that for you .
 if the ECM isnt shooting a code other then 12 then there is mostlike a problem with one or more of the sensors

I wonder if the ECU could be bad? Not sure how to test for this.

 I have driven it a few thousand miles since the swap. When i start it the light stays on for a moment and then goes off like normal.

The ECU doesn't always realize there's a problem & throw a code when it's broken. Just a thought.

The ECU doesn't always realize there's a problem & throw a code when it's broken. Just a thought.

yep very true exspecialy with older ECM's . if the sender completely dies . the ECM simply will not recourd information  and make adjustments  that the falty sender would be telling it to make .
 this is where running a OBD scan  comes in . you can eather go through and test each sendor  or have the test code run . this will tell you if a sender is not sending info to the ECM  IE its faulty or  it has a  wiring issue . there also is alot of  other issues past  bad or faulty sendors that will kick the ECM into fail safe mode . running an OBD  scan  will only give you information on the electronics . in wich case it will help you narrow down the possable problems


JT over on the suzuki forum has a good write up on this as well as how to  check the senders . he exsplains it much better then i can  and is much clearer .
 im not sure if  it acceptable to post such a link here  on this forum  though as some places frown on such things . so if you would like the link  i would send it to you in PM