Please help, my car is running extremely rich, to the point that it burns your eyes. Its running rough at idle and stumbles when trying to take off. I think it may be the O2's but not sure.

With the key on (not running), I checked the voltage on both sensors. They both started at about 450mv but slowly creeped to 900mv over a period of about two minutes. With the car running in open loop, they were bouncing on both sides between 800mv and 900mv and the car ran pretty good. When it hit closed loop, i could hear the rough idle come on and both sides rapidly dropped off and fluctuated between 200mv and 300mv.

The car has run great with no problems for the last year. The only thing that i have done to the car recently is change the collector gaskets because they were starting to leak. Here it's a week later with no leaks but the car is running like sh@#!

Any insight would be greatly appreciated. Thanks

 

When you worked on the collectors, did you spray penetrating oil on the bolts? Any chance it soaked the outside of the O2 sensors?

 

No, I didn't use any penetrating oil. The O2's are a year old with about 10,000 miles on them. The only significant changes that I can remember are: 1) using rtv copper on the collector gaskets and 2) about a month ago i filled the tank before a night at the track with 100 octane unleaded race fuel. However, I thought that both were O2 sensor safe. Is it possible that either of these could damage an O2?

By the way Injuneer, I've read your scan master page, it's excellent. I have to get one of those. While I know it's not recommended, I used a multimeter....it's all I have. I'm still a little confused though on what normal readings look like. From reading on the board, I was under the assuption that, with the key on, the O2 should read a steady 450mv. Mine started there and then rose. Is this because when you apply power to the system the O2's start heating up? Does what I described sound like normal operation?

One last thing, I've already checked for the common problem areas such as burnt wires, exhaust leaks, and maf, intake, and ducting leaks. Everything looks good and most of the parts are new from the head and cam swap last year. The car also has a new opti. Thanks to all who may help.

 

I hope this is posted on the right board. Should it be in the computer diagnostics section?

Also, I was following a haynes book for proper operation of the O2's. It said the resistance should be between 5-7 ohms. My left bank measured 4.1 ohms and the right side measured 4.4 ohms. While running, the readings were the same on both sides, is this an indication of anything. Thanks.

 

How many miles are on those O2's? Maybe worth changing them just to make sure....

 

The o2 should read roughly .870 to .9 something normally.As you know they aren't very accurate compared to wideband o2s.But still if you are getting .200 to .300..that is super super lean not super rich..and you would likely be throwing codes like crazy for too lean or too rich.Does your car have a cat..headers..Headers on the ls1 cars without tuning make the cars run very rich..not sure about lt1 cars.I would think you are either reading the wrong o2s..you want to only read the front ones..they are the ones that should go into the range said.If you are in the high 900s then you are indeed rich usually.

And you don't check o2 at idle you check them at wot.They will be constantly cycling and stabilize at wot.Of course they don't control the car at wot..but they give you a rough indication of your air fuel mixture.

If you have lots of miles like over 60,000 I would change them out but make sure you only change out the front o2s..the backs don't matter and you can put sims in there if you want..the backs only monitor the cats.

 

The o2's in the car right now have about 10,000 miles on them, I put them in last fall. The car is a 94, there are no rear o2's. It only has two.

Are there typical indications for a contaminated O2? Do they degrade over time or will they just die? Are the readings I'm taking so far off because there is another problem and the O2's are just trying to compensate? I'm at a total loss and am trying to learn how these sensors interact with the computer.

I also tried to get it scanned but autozone couldn't do it. I guess I'll try to take it to the dealer where they can access the computer.

 

Well 02 shouldn't be bad in that few miles..unless you run leaded gas or the car has been superrich..as said headers do that in ls1 cars usually so if you haven't tuned and leaned it out possibly same deal in your lt1.
And as said only the o2 before the cars or right off the exhausts matter to the way the car runs.