Im trying to read my O2 data with my scan tool. I read that the voltage is supposed to fluctuate from .1-.9 Volts no less than every second. If the voltage is from .1-.5 than it is reading lean, if it is from .5-.9 than it is reading rich. This is my basic understanding.

It looks like my post sensors are reading rich and my pre sensors are inconsistant. I am trying to figure out a slight misfire issue which has been pending a p03000 code but never actually throws the code. That will come and go, but it does run sluggish so I know there's something wrong.

Take a look at my 02 data: https://picasaweb.google.com/1121999...46165909567842

Any input is appreciated, thanks!

 

The post cat sensors only look at what comes out of the cat, and the PCM does not look at that data to determine the A/F ratio, it only uses it to see if the cat is working properly.
This article may help.
Too much or too little air can mess with today's systems | Search Autoparts

 

The pre-cat sensor readings don't look bad from here. As Z28 Pete says (I guess I'm L32 Pete, LOL) it is the pre-cat sensors exclusively that are used to control the air-fuel ratio (via injector pulses). You're getting good range (.1-.9 V) but I can't tell the activity level. IOW, how many times does the voltage reading cross .45V. A tired O2 sensor will not be very active.

The post-cat sensors should show a steady reading around .45V and that indicates that the cat is doing it's job, cleaning up the exhaust gases. Your post-cat readings do look richer than I'd expect to see and also show too much variation.

How many miles on the engine/cats? Was it run with any problems for a while that might have damaged the cats?

 

I dont know much about the car, i just know it's been parked for a long time. It has an aftermarket exhaust system with headers, cats and a single muffler. The IAT wiring was broken, so it must have been running rich before I fixed that. Other than that it still has a slight misfire I am trying to troubleshoot. The voltage fluctuates about every second but is sometimes inconsistant with the voltage if you notice my other pics.
I have an infared heat gun, I can probably get under the car and test the cats. Is there another way to test them?

 

Found a great article on reading sensor data

MOTOR Magazine Article | MOTOR Information Systems

 

Do you guys think it's reading rich on the post cat o2 because of a possible blocked/bad cat?

 

The purpose of the post cat is not to determine if the engine is running rich or lean. The output of the downstream O2 is to check the condition of the cat. If the downstream cat follows the output of the upstream cat the PCM assumes that the cat is not cleaning the exhaust. The proper way to determine if the cat is clogged is with a pressure gouge plugged in place of the upstream O2. If the pressure is above about 4 PSI you can conclude that the exhaust is clogged, cat, pipes, mufflers, etc..

 

Ok that makes sense, thanks for the info!