98fourdoor

Upstream o2 reads air/fuel ratio and let's the ecm adjust accordingly. Downstream ONLY measures catalyst efficiency. When watching the o2 sensors with scan-tool the upstream should constantly switch between lean/rich readings. Downstream should read steady showing proper converter operation. If downstream is switching high/low like upstream you have a bad catalytic converter. I know many members here wont care but im an ASE certified master technician. Its the same concept for every vehicle. But just because o2 sensors are reading off doesn't mean bad sensors,it could also be showing problems with the engine causing rich or lean conditions.

sems

X2 on what he said. Downstream is only checking if the catalytic converter is doing its job. I am also a Journeyman Automotive Service Technician.

But back on topic. Great to hear the OP has their fuel mileage back up. Gotta love it when you put some money into your jeep and it starts paying you back!

Aaron N.S.

I have to ask, I'm building my Jeep as a offroad only vehicle, besides MT is a non-inspection state, but if the rear sensor only is checking for efficiency what going to happen if the cat is completely removed? On my truck I'm sure it's plugged for now am not looking to do a complete exhaust system yet.

dukie564

It's going to throw a CEL if you remove the CAT.

And it doesn't matter if your state is an emissions check state. Under Federal Law it's illegal to modify/remove the emissions system on a vehicle, regardless of vehicle use.

Furthermore it's against forum rules to discuss removing it.

98fourdoor

With no cat you will always have a low efficiency code. Wont affect the operation of the engine. But as stated it is highly illegal to remove emissions systems on any vehicle. But we can't tell you what to do with your own vehicle and I doubt anyone here is going to report you. Haha

jcwclm

Battle of the schools!

foxmxrcer

When I read the statements of the UTI kid, I just face palmed myself. I go to ATC, UTI's rival school, and they dont teach us those lies over here

Kmart164

UTI is a joke. You know, Wyotech being a school that barely advertises, and has to turn kids away because they fill up so fast, every year, is the BEST school in the industry.

All's I see on UTI's commercials is flash, and BS. You won't get to Dyno a Blown Hemi Cuda in the automotive program.

Crock of crap.

Proud Wyotech Screamin Eagle!

N20jeep

I have not been impressed with some of the wyotech grads I've worked with over the years. Just my opinion

dilljeepo

So Wyotech doesn't teach you how to form your thoughts into a coherent statement huh? What a shame. Roasting some guy for going to a different techincal institute is so petty and pathetic. I just wanted to say that because I beleive that cyber-bullying has more of an impact than anyone cares to acknowledge. Saying that to someone's face could lower their self-esteem even when they know they are doing well in post-secondary schooling. Grow up and drop your self-pride a little bit, because it's embarassing.

wildbill1

Gaining that much fuel economy is great. I have a '99 XJ that I bought last August. When I got it, it was getting about 14-15mpg average. I have since changed the injectors to 784's, installed the Accel tune up kit (plugs, cap, rotor and wires) and ran a can or Seafoam through it. I also cleaned my throttle body and IAC.

My last tank averaged 18.8 mpg. I'm very happy with that. I don't hear of too many people getting better than that.

jcwclm

How about we all quit the smashing of schools. Real knowledge comes from experience.

dukie564

seriously

just because you basically took an intro course to a wide range of things doesn't mean you actually know what the hell you are doing. Experience is the only way to gain real knowledge.

dukie564

back to the topic

Northwoods Snowman

To the OP again, what did you end up putting on, where'd you get it, and how much did it set you back?