Heres the situation, replaced the cat. convertor with a test pipe that has a slot for an 02 sensor to be screwed into. I put my old rear o2 sensor into this and ran the jeep fine for a while, until one day, that wiring ripped straight out of the top of the o2 sensor. Now i just ordered a new o2 sensor, and i was wondering if it will run very rich if i put it back in the test pipe resulting in bad gas mileage still. Or, i read somewhere about someone who mounted the sensor completely outside of the exhaust system to sense a vast amount of oxygen (since this is the rear sensor, and more oxygen=cat. converter working better), would this be a good idea, or would it make the jeep run too lean, and possibly blow it up?

 

JMO but I'd put the sensor back where it belongs. That will prevent the ECM from receiving an incorrect signal. Mounting the o2 sensor outside of the exhaust could possibly tell the ECM that the engine is running lean, or that there is a sensor malfunction, sending it into closed loop mode.

 

Well, when its in the test pipe, its sensing that the cat. converter isnt working, since there is none. This will result in bad gas mileage, will it not?

 

How so?

 

Its sensing that the cat. convertor isnt cleaning the air correctly, since there is none. Correct me if im wrong?

 

Okay that's a given, but just what exactly is it sensing when it's mounted "outside" of the exhaust system altogether? No combustion by-products whatsoever. What signal will that send to the ECM? Engine not running? It contradicts the front o2 sensor entirely. At least IN the exhaust it will still get readings.

I avoided this whole issue by installing a high performance converter in my '97 ZJ 5.2 and got the best of both worlds.

 

why'd u take out ur cat to begin wiuht?

 

yeah you are not going to see a huge gain removing it i would rather leave it in and not screw up my readings.

 

The old cat was rattling around inside. Scraped it and bought a test pipe. I really dunno why I did, probably to save some money.

 

i suggest getting a new cat and doin it correctyl cause over time ur gonna mess up ur jeep cause the pc wont be getting the right readings and it'll make it run lean or rich and its just not good, im not looking at this in a tree hugger way, i just really care about cars and having them run correctly lol

 

You can get a high performance cat cheaper than you think. Mine cost about the same as a performance muffler- $165 bucks. The difference in power from the old worn out cat to the new one was amazing. It even changed the sound. No other changes were made at that time, so I know the cat made the difference. The o2 sensor's are still in use, and the emissions actually improved according to the test.

 

x's 2. I bought a Magnaflow converter from SummitRacing for less than $115. My old one was rattling and sounded terrible. The new one made a huge difference in performance. Plus...everything still works as it should. Even though we don't have emmissions tests here, the day is coming...

 

Okay, i know a high flow cat would help, but thats not helping my current situation. I was reading that the o2 sensor only sends a neutral signal to the computer until it reachs 600 degree F, and that the computer uses a neither rich nor lean mixture during the period before it reaches this tempurature. If the sensor was outside of the exhaust, and never reached the temp, thus never taking oxygen readings, would the computer just use this neutral signal all the time? or would it eventually spit a code for the o2 sensor never warming?