O2 sensor problems

[TimF]

well according to my moms bf(the former owner of my talon) the O2 sensor is not working. So he said the car runs as if it is warming up, and it uses more fuel. He had the sensor changed out and a couple of other reapairs to try and fix it, but it still out, the car starts fine, drives fine excepet for if you cruise the check engine light comes of, but you just let of the gas and i goes away. Also in idele the car revs and drops like VRMMMM vrmmm VRMMMM vrmmm. Yea but he told me the O2 does not work and it runs rich(which is killing mpg, i get 16 city) Any way to fix this?

 

[XiKeiyaZI]

If it is not working, then you likely either have not slipped into Closed Loop Mode, or you have damaged wiring running from the 02 Sensor plug to the ECU.

First, you need to verify that the 02 is not functioning properly. There are a few ways to do this, but the easiest would be to get the car up and running, warmed up, then unplug the 02 sensor and see if the car begins idling differently. This pulls the 02 out of the equation for a moment. If it doesn't change, the 02 is not functioning.

You should pick up a logging method, be it a Palm or Link. This will allow you to verify that your car is going into Closed Loop Mode. Closed Loop Mode relies on a few requirements being met, and one item in particular that I had trouble with myself was : Coolant Temp. My CTS was bad, so I changed it out and viola' Closed Loop.

For now, let's go ahead and focus on one thing at a time. Closed Loop and Wiring Confirmation would be ideal to start with. Verify your wiring is alright and that you're entering closed loop.

 

[nehring8]

when the car is warmed up and running, probe the two signal wires on the O2 sensor, usually black and white, it shuld read around .5V and should be moving from around .4 - .6 volts, if it is then the O2 sensor is OK....could also have a cracked exhaust manifold (like most) which is letting the O2 sensor see too much air and the ECU is trying to compensate by adding more fuel...

 

[TimF]

so if my manifold was cracked would i be able to tell my looking at it? or is there a way to test? i dont have any testing tools really

 

[XiKeiyaZI]

Want to see where your exhaust leaks are? Do a Seafoam test.

Have someone in the vehicle keeping the RPM's at 2K. Take a hose off of the throttle body and suck a tad bit of seafoam from the can into the throttle body. The engine will bog, won't hurt it at all, and the person in the car needs to keep the engine running. If you have an exhaust leak, there will instantly be smoke everywhere under your hood.

Seafoam treatment is also a good thing for high mileage cars with a lot of carbon buildup. It's not water-based so you won't be hydrolocking your engine.

 

[TimF]

so im guessing that if there is no leak it will vent out the back of my tail pipes like normal

 

[XiKeiyaZI]

so im guessing that if there is no leak it will vent out the back of my tail pipes like normal

Correct-o

 

[TimF]

well I talked to my mom boyfriend, he said he took in the Talon when he owned it and had the O2 replaced and rewired and the problem still exists, he said the mech told him the ECU was bad no the Sensor or wiring.

 

[XiKeiyaZI]

Well, then you have some sort of lead, regardless of how accurate it may be. Pull the ECU, open it up, and take some pictures. Look for anything burnt, brown, or if it smells funny.