Cat free

[opy]

I have no cat on the old beast (off road us only?). The truck runs rich, I am assuming because the cat is gone. The O2 sensor was put back in the new pipe where it would have been in the cat. Any suggestions to correct the mixture?

 

[BigGreenBronco]

i wanted my truck to sound rich and loud too i cut off the cats and there was an 02 senser at first the engine light stayed on but when i had pipes welded it cuttoff i assume that the 02 sensor only checks for back pressure but then again im not a mechanic

 

[Xxxyank]

i wanted my truck to sound rich and loud too i cut off the cats and there was an 02 senser at first the engine light stayed on but when i had pipes welded it cuttoff i assume that the 02 sensor only checks for back pressure but then again im not a mechanic

Basically the O2 sensor measures the exhaust for combustibles & sends a signal back to the ECU which adjusts for the excess fuel or air, depending on what the O2 reads... there are different types, of O2 senors as well, but they all basically do the same...

If the vehicle is designed with an O2 sensor, it is best that you always have one, unless you redesign fuel/intake. Or your vehicle will always run either to lean or rich, which will cause internal engine problems...

 

[Xxxyank]

I have no cat on the old beast (off road us only?). The truck runs rich, I am assuming because the cat is gone. The O2 sensor was put back in the new pipe where it would have been in the cat. Any suggestions to correct the mixture?

I'm not a Bronco expert & i couldn't tell you without actually looking, what you may have & where the location is...

But if you have a heated 02 sensor, then i would check your connections... If you don't, then i would either upgrade to a heated one (which is more expensive) or want to consider moving the O2 sensor closer to the manifold... The reason why they normally place a regular O2 sensor down by the Cat, is cause it heats the 02 sensor up quicker in-front (back pressure) or on a cat, so there is no need for heated one... If they place it closer to the engine, they normally just put a heated 02 sensor in.

Most exhaust guys (or a real mechanic) have dealt with stuff like this for years, if you know of one, he could probably head you in the right direction of what you need to do. But it is a common problem when changing the exhaust in that manner. Good luck

 

[50joe]

In a 92, it is a heated o2. Any 4 wire O2 sensor is heated, one wire is not. They are NOT interchangable either. Older trucks Utilize a single sensor just after the meet in the Y pipe. Newer trucks use 2, one on either pipe just off the manifold. The upstream O2, (pre cat) is the one the ECM uses to control the air fuel ratio by reading exhaust gases. If it senses the mixture is rich, it decreases the fuel trim to lean it out, and vice versa. Any O2 sensor after the cat in our case, or in the cat itself in some cases, does nothing but basically "tattle tale" on the catalytic converter and the upstream O2. If the cat is not doing its job (96 and newer only), the downstream (post cat) sensor will tell the Ecm and trigger the check engine light. Also, if equipped with the downstream o2, if the ECM changes the air/fuel mixture and see's no change in the upstream O2, it uses the downstream values to determin if the upstream sensor is bad, or if there is another maechanical failure.

Now, the reason for the heaters: Older fuel injection used a one wire, non heated sensor to control the mixture. The problem with that was, the sensor had to be warmed up to read accurately. When it was cold, the sensor would remain in "open" loop, and the ECM used a default value. Once the sensor warmed up, it would switch to "closed" loop, and read the gasses from the sensor. Manufactures started using the heated O2 to reduce the amount of time it took the sensor to reach closed loop, allowing the fuel injection to run more efficiently faster.

Non heated sensors do not have the wiring OR the programming in the ECM to turn the heater on, so thats why you cannot switch between the 2.

As in the case with your peticular truck, without a scanner plugged in to see what its doing, I would venture a guess that if the sensor was still installed during the cutting and especially the welding, it may have shorted out causing your sudden rich condition. A long read, but knowing how to change parts is only half the battle. Knowing WHY you may have to change them goes along way in helping you understand how stuff works. Hope this helps a little....

 

[BigGreenBronco]

Basically the O2 sensor measures the exhaust for combustibles & sends a signal back to the ECU which adjusts for the excess fuel or air, depending on what the O2 reads... there are different types, of O2 senors as well, but they all basically do the same...

If the vehicle is designed with an O2 sensor, it is best that you always have one, unless you redesign fuel/intake. Or your vehicle will always run either to lean or rich, which will cause internal engine problems...

The o2 sensor is still on the truck i just dont have any cats