O2 sensors keep going out

I keep having a problem with my two front (upstream) O2 sensors going out. I have a cat delete and when I had the car tuned I had the rear O2's deleted. Twice now I replaced my front O2 sensors and at 70.00 a pop I'm getting pissed. Could the tune be the problem? When I replace the sensors my ses light goes out and after a few days it's back on again. The car runs rich and the fuel mileage goes out the window, I also notice a decrease in performance. The car doesn't run rough but the code reads upstream O2 sensor bank 1 bad/rich. I still have the stock manifolds on the car as well. Any help is greatly appreciated.

What brand sensors and are you utilizing an extension harness?

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Originally Posted by pajeff02

What brand sensors and are you utilizing an extension harness?

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I'm using bosch oem direct replacement O2 sensors and no extension harnesses

Most members have had great luck with the Bosch 13111's in their LT's -- I run the same setup. Any chance you have a wiring issue? Are codes being thrown for both banks? Can you read your air/fuel ratio or fuel trims?

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Originally Posted by pajeff02

Most members have had great luck with the Bosch 13111's in their LT's -- I run the same setup. Any chance you have a wiring issue? Are codes being thrown for both banks? Can you read your air/fuel ratio or fuel trims?

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Actually yes, codes are being thrown for both banks and saying running rich. Thats why I just replace both O2's. I also think I have a small vaccum leak as I notice the car holds on to the rpm's when I let off the throttle. could that cause an issue? I don't think there is a wiring issue as the car never acted up until after the lap top tune I had done. I know the tuner messed with the timing and air/fuel ratios

Ive heard running rich can burn out o2 sensors, however im still running 2 stock o2 sensors on extensions and they arent burning out at all. Longtubes to a 3 inch x pipe with no mufflers and dumped and have yet to burn one out. When i had the x pipe put in they broke one but i replaced it and havent had a issue since. Dunno what to tell you but if all you have are headers and no cats it shouldnt be burning o2s out. I wouldnt throw the o2 sensors out that keep burning up, i hope your taking them back as "Defective". My advice if you did put headers in the car would be to get a tune, youve almost blown through 200-300 bucks as it is.

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Originally Posted by dennis ss

Actually yes, codes are being thrown for both banks and saying running rich. Thats why I just replace both O2's. I also think I have a small vaccum leak as I notice the car holds on to the rpm's when I let off the throttle. could that cause an issue? I don't think there is a wiring issue as the car never acted up until after the lap top tune I had done. I know the tuner messed with the timing and air/fuel ratios

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Any additional air entering AFTER the combustion chamber will cause the O2's to read lean and result in fuel being added to the engine. Any vacuum leaks would add air BEFORE the combustion chamber and result in a lean condition as it is being introduced after the MAF.

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Originally Posted by pajeff02

Any additional air entering AFTER the combustion chamber will cause the O2's to read lean and result in fuel being added to the engine. Any vacuum leaks would add air BEFORE the combustion chamber and result in a lean condition as it is being introduced after the MAF.

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So a vacuum leak wouldn't be the culprit then. I wonder what the deal is. I guess it's time to go to a shop.

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Originally Posted by 95camaroZNC

Ive heard running rich can burn out o2 sensors, however im still running 2 stock o2 sensors on extensions and they arent burning out at all. Longtubes to a 3 inch x pipe with no mufflers and dumped and have yet to burn one out. When i had the x pipe put in they broke one but i replaced it and havent had a issue since. Dunno what to tell you but if all you have are headers and no cats it shouldnt be burning o2s out. I wouldnt throw the o2 sensors out that keep burning up, i hope your taking them back as "Defective". My advice if you did put headers in the car would be to get a tune, youve almost blown through 200-300 bucks as it is.

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I don't have headers on the car, I only have a cat delete and still have my stock manifolds on the engine. I had a tune done already and was wondering if maybe he screwed something up.

Other things that can make the car run rich: A real dirty air filter, an obstruction in the intake, a bad Engine Coolant Temperature (ECT) switch, excessive fuel pressure, leaking injectors, etc. Know anyone with a scan tool?

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Originally Posted by pajeff02

Other things that can make the car run rich: A real dirty air filter, an obstruction in the intake, a bad Engine Coolant Temperature (ECT) switch, excessive fuel pressure, leaking injectors, etc. Know anyone with a scan tool?

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Yes. My friend scanned with an sct tuner. Thats what told me about the banks 1/2 O2's running bad and rich. No other codes came up

Which bank keeps going bad, is it bank one bank two or both?

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Originally Posted by 95camaroZNC

Which bank keeps going bad, is it bank one bank two or both?

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Both banks, upstream O2 sensors. I just replaced them last night and reset the computer by disconnecting the negative terminal on the battery and this morning the ses light is back on again :brick:

You do know you dont have to reset the computer each time, its really not doing much for you at all, the lights still there you just have to travel 30 miles for it to cut back on and the system to completely reboot. So your light has to do with something other then your o2s. Bad wiring or something somewhere possibly also do you have your sensors from the rear still? If so swap those with the front ones assuming they werent bad and see if that does anything all the o2s in all 4 banks are the same. Further more if you can to pin down this problem more possibly, take pictures of where you put the o2 sensors in. Might not help me very much but someone else might see something wrong and be able to help with this problem more. Also when you had the o2s popped off did you have them kill the EGR as well? Lastly is the car running choppy or is it jerking at all when sitting at a stop?

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Originally Posted by 95camaroZNC

You do know you dont have to reset the computer each time, its really not doing much for you at all, the lights still there you just have to travel 30 miles for it to cut back on and the system to completely reboot. So your light has to do with something other then your o2s. Bad wiring or something somewhere possibly also do you have your sensors from the rear still? If so swap those with the front ones assuming they werent bad and see if that does anything all the o2s in all 4 banks are the same.

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The rear O2's are there but I had them deleted when I had the car tuned. There are no other codes coming on other than the ones stated earlier. This is a pain. I just bought and installed the new bosch O2's last night, I don't know what else to do

what are the actual code numbers?

Well the ses light went out on it's own and has stayed off for a full day now. Maybe the computer need time to adjust and get the proper readings from the new O2 sensors? I will keep you posted on how it's going.

Its supposed to notice i think after 1 cycle if the fuel mix is off. But def keep us posted.

It's possible for a bad or aftermarket MAF to cause a rich condition correct??

I've heard or read that even though you are actually running lean, the PCM could be overcompensating for a lean condition which would be sending too much fuel into the mix causing a rich condition.

Another day and no ses light. Car is running noticably better. Performance is back and all is good. Thanks to all for the advice

Man my car is doing the same thing :( the ses light comes and goes with 02 sensor codes but i do have a small exhaust leak right at the head/headers and i think that is what's causing it

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Originally Posted by silverWS.6

Man my car is doing the same thing :( the ses light comes and goes with 02 sensor codes but i do have a small exhaust leak right at the head/headers and i think that is what's causing it

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That sounds like your problem. I doubt your sensors are bad, they just can't get an accurate reading. I fixed my problem and all is well so hopefully it will stay that way

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Originally Posted by pajeff02

Any additional air entering AFTER the combustion chamber will cause the O2's to read lean and result in fuel being added to the engine. Any vacuum leaks would add air BEFORE the combustion chamber and result in a lean condition as it is being introduced after the MAF.

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Originally Posted by silverWS.6

Man my car is doing the same thing :( the ses light comes and goes with 02 sensor codes but i do have a small exhaust leak right at the head/headers and i think that is what's causing it

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:D Fix your leak. If your car runs too rich too long, you'll end up not only fixing your exhaust leak, but also replacing your O2 sensors. You'll probably see an increase in fuel mileage by fixing it too :)

My car keeps popping the 1311 and 1511 codes.....just changed to the bosch 13111's re-tuned the car and it still set them off!!! This is the 3rd set of O2's and tune.....:growl:

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Originally Posted by 35th-ANV-SS

It's possible for a bad or aftermarket MAF to cause a rich condition correct??

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Bad? Sure.
Aftermarket? No likely...they tend to lean you out more than anything to get their 'claimed' power gains.



What exhaust is on the car? Any chance the O2's are getting fresh air?
Are the ones you are purchasing heated units?

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Originally Posted by Mr. Luos

Bad? Sure.
Aftermarket? No likely...they tend to lean you out more than anything to get their 'claimed' power gains.

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I knew they leaned you out...but I didn't know if it was possible for the PCM to add too much fuel from the lean condition actually putting the car into a rich condition or...I've thought I seen where the MAF will give a false reading where the car thinks it's running lean when it's actually not and thus the PCM dumps more fuel to compensate making it rich.

Or...I could be blowing smoke up my ass too :lol:

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Originally Posted by 35th-ANV-SS

I knew they leaned you out...but I didn't know if it was possible for the PCM to add too much fuel from the lean condition actually putting the car into a rich condition or...I've thought I seen where the MAF will give a false reading where the car thinks it's running lean when it's actually not and thus the PCM dumps more fuel to compensate making it rich.

Or...I could be blowing smoke up my ass too :lol:

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I get what you are saying.
But the computer will tell you it is lean as it is dumping fuel to make up for it.

If he is getting the 'too rich' code, the computer is actually pulling fuel but still getting too much at the O2's.