Hi everyone I have an issue with my left hand side 02 sensor failing in my 97 c5 after getting a lot of engine work done , big cam , head work, bigger injectors , bigger fuel pump , full exhaust system , stall converter and a tune . The first time it happened it started running rough like it was a bit flooded when it was cold but then when it got up to temp it came good but then after a few days it turned completely on its head and would be ok when cold but when it got up to temp would shut down and was not drivable . Was throwing all types of codes but turned out it must have richened itself up that much it then went way back the opposite way and backed off the fuel 30 % to the left bank so then it wouldn’t go. After transporting it back to the guys that did the work they eventually worked it out , cleared the codes, changed out the 02 sensors that were put in new with all the work and it was good to go.

About 2000 ks past this played up again , running extremely rich , back firing and carrying on like a flooded engine does ,changed the 02 sensors again and cleared codes still ran rough like engine was flooded and it wouldn’t keep running . I didn’t have time to pull the plugs and shoot the fuel out of the cylinders so just let it evaporate over a couple of days , put a new battery in it as the other one was no good and it ran fine .

Aprox another 2000ks has past and the other night was driving it and it started playing up again backfiring but then after a while it came good and got it home , started it yesterday running ok till I went to drive it then was playing up backfiring so just did the block and put it back in the shed as this time I don’t want to get it to the stage it’s undrivable and flooded .

Always seems to be the left side of the engine playing up and can comfortably confirm this as I don’t have a H pipe or X pipe in the system . When changing the sensors I always change both . This was never an issue before the engine work got done . Living in Australia there aren’t many c5’s over here so to get someone that knows them back to front is pretty much nonexistent .The place that did the work is a very reputable shop and no expense was spared in doing the engine work, every seal and gasket was replaced as I didn’t want to have any issues but they are getting out of ideas why this is happening. Hopefully someone on here maybe able to help me out on what might be causing this.
Thanks for taking the time to read this long winded post it just wanted to put all the info in as this has been quite a saga since the work got done .

 

First thing where did you buy these sensors ??…if someplace like EBay or Amazon that may be your problem…if OEM quality it just may be the sensor used…when I had my 01 it didn’t like Delphi or Bosch…Denso’s worked fine…if running rich it may be a wiring issue and not an actual rich condition…if the signal wire is shorted to ground the PCM will see a lean condition and then increase injector pulse…if you have a scan tool let the O2 sensors cool down and also remove the O2 heater circuit fuse…now turn on the ignition…the O2 sensors are biased at 450mv’s so you should see that on the scan tool…if the heater fuse is installed the heater will start heating the sensor and start bringing that bias voltage towards 200 mv’s or less…if you see 450 mv’s you may want to shake down the wiring and see if it goes from 450 to somewhere near ground…450mv’s means the signal and signal ground circuit is good.

 

thanks for the info . The first 2 lots of sensors the performance shop got them I’m not sure on the brand of the first one but the second lot were Delphi technologies and the 3rd lot are NTK that I got from my mate that runs and owns a parts shop. I don’t have a scan tool I just normally use the one on the car . Which scan tool would u recommend and where to buy it from . I’m happy to get one to try get to the bottom of this issue so I can get the car back to being reliable like it was before all the work got done . I’ll also get some denso ones in the meantime and give them a try .

 

Autel and Launch are 2 of my favorite aftermarket scan tools and you can pick one up on Amazon…just don’t buy one from a 3rd party supplier as you will have trouble with the warranty if you have problems with it…this one is almost 700 Australian dollars…the cars “code reader” only shows you the trouble codes and not the information you need…you want one with bidirectional capability too which this one has.

 

Sounds like that tune has some issues. Also, what kind of fuel are you running? (octane rating, ethanol content, etc.)