Had a service engine light that would always come on after a couple miles of driving. Obd1 Code read driver side 02 sensor. However the car always ran great for years. I finally decided to replace it and it runs terrible and trips service engine light randomly. Ironically when the light comes on, it run better. I purchased a Denso o2 which was suppose to cross ref , but I am guessing it is NOT right at all. The only Number I could read on the original
o2 is a number 327? It has hooker headers and a Borla dual exhaust and has been a strong running car since I bought it in 2009.
Not sure if I could order stock GM AC Delco or because of the exhaust mods that were done by prev owner I need special O2 sensors.
Also should I replace both.
Also looking on EBAY, they look very similiar to the stock AC Delco .
Thanks

 

Do not get any from Ebay, I bought some and they failed right away. They were breaking into pieces inside the sensor. I have Bosch and haven't had any problems, don't know if anyone has or not.


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Why do you need "special" O2 sensors?

AC-Delco AFS75 is what you want.

 

ok thanks AC-Delco AFS75 is what I will buy. Should I replace both or just the bad one ?

 

alot of people report hit and miss luck with the bosch. Ac delco is preffered by most. One thing to realize is what they do- they read the exhaust and then make fueling changes based upon the reading. Therefore if the reading is getting messed up from exhauast leaks before or near the o2 sensor it will make fueling corrections based upon false info. Be certain their are no exhaust leaks. Misfires will do similar- be sure not misfiring. The reason it runs better when the sel light comes on is because it is probably kicking you back into open loop and then the fueling corrections are not happening. It may be the sensor or it could be exhaust leaks or misfires,etc. It might be helpful to provide the actual code. It might be helpful if you have the way to moniter data.($60 cable and laptop with software installed).


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The sensors should come with a coating of conductive anti-seize compound. Do not add any more. You can contaminate the sensors with too much. Keep the outside of the sensors clean, and not exposed to fluid drips or exhaust leaks. The sensor needs to access outside air so that the "thimble" which is the actual sensing element can compare the oxygen content of the exhaust on the outside of the thimble to the oxygen content of the ambient air inside the thimble, and generate a voltage based on the relative concentration of oxygen. Oil drips, power steering fluid drips, etc can destroy the sensors.

 

ok I ordered a innovia 3120 and should have it by Monday. I noticed an exhaust leak on the slip joint of my Hooker Super Comp headers. This leak is about 2 ft from my driver o2 sensor that I just replaced. It appears to have blown out an orange colored rubber silicone from the slip joint. Some one must have used to seal a long while back before I owned the car. I am guessing this could really screw up the o2 reading causing my problems.
When i pulled the PCM batt fuse the car ran great for about 45 min then back to rough. Could the computer have taken that long to readjust the fuel and screw it up ? thanks for any help !

 

I am not quite getting a good picture of you sensor location. On my headers the sensor is very close to the "slip joint" as all of the tubes collect right there and then perhaps a foot or so of pipe were the y pipe would connect(branch to xpipe on my setup) Is the sensor upstream from the collector(my assumption but 2 feet seems far). Personally if sensor is that far upstream(closer to head) then that leak may not be affecting the reading at all. If the leak is before the sensor or very close then it would effect sensor. If your sensor is 2 feet from were the tubes merge on the header it seems too far back so guessing its the other way. Take a good look at the wiring going to sensors as may be burned and also look at your extentions(are they plug in extentions or perhaps someone tried to splice wires to extend). It does take the computer a while to relearn especially if your hitting multiple cells. The fuel correction would grow (to my understanding) from the max allowed in the short term as the long term adds or subtracts fuel. So as the long term grows the amount of fuel correction grows until it drops the short term.


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my o2 is on header and is 5 inches in front of collector flang. slip joint is on number 1 cylinder pipe approx 18" from head and approx 15" from o2 sensor.
waiting for my 3120 obd1/obd2 tester to arrive ! thx for any further input from all !

 

Yep that would effect things the bigger the leak the worse it will too. I recall reading about it when I was researching ways to seal the slip fit from header to my main exhaust. Most people who had leaks had temperary results with the copper rtv. I think some used bandclamps as well. I think some just weld it up but have to tack it in place while bolted and may have to remove steering shaft. I really dont remember but I do know there was several threads. What worked for me was a hardening exhaust patching compound. I used a layer of it towards the end of my connections(so none would end up inside of tube and would aid in future disassembly-assembly). Then I spread a thin layer over outer pipe and used my band clamp. I may not have needed to add anything to seal but my narrow bands were inches away from the joint and my widebands were behind the joint so I didnt want any leaks. My guess is using clamp and the copper rtv will be an ongoing repair but short of welding it up may be the best solution. I did read of someone recomending aluminum foil wrap around joints under the band clamp but never tried it.


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