Hello, I am working on my 95 Base model. 3 days ago on the way home from work I was running EEhack because I have been having some odd idle issues at a stop in closed loop. After a few minutes it went into closed loop and the right bank O2 sensor was still sending a signal but the trims went to +25% and stayed there and the left shot to around -15%. Car ran ok though.Seeing that they are original to the car at 74000 miles I decided to replace them. Full disclosure I bought cheapo's on Amazon. I replaced both left and right pre-cat sensors and now they are stuck at the base 457mv and the car won't go into closed loop. Stayed in open loop for 30 minutes or so. I guess it's not impossible to get 2 bad O2 sensors but it seems unlikely. Was I supposed to do anything to tell the computer they are new or something? Also still idles really low.

 

Did the old sensors do the same thing as the new cheap ones? Also, what idle issues are you having at a stop? Could be an exhaust leak affecting the O2 readings

 

Do you have factory exhaust? Many times on new exhaust the sensors do not fit back because they are short and people buy these extenders If these are at 90 Degree angle , they play hell. Something to look at.

 

No, they actually jittered up and down like normal until a few days ago. See the pics below for details. For the idle problem it runs great, I mean like a champion until it hits 185 deg on the water temp then at idle it drops to around 450-500 RPM, oil pressure goes all the way down, but no lights come on, and the volts flutter up and down as well as feeling the shaking through the car. I replaced almost all the hoses, did a smoke test and a starting, running, and kick down vacuum test, soap bubble pressure test and cannot find any leaks. I basically have to shift in neutral at red lights and stop signs and keep pressure on the gas or I'm worried the engine will starve without oil.

As for the factory exhaust, yes it's bone stock.

I bought this in rough shape and wasn't taken care of so I replaced almost everything cause it barely ran when I started this past January. This includes MAF, MAP, Coil, Control Module, EGR Valve, Optispark, head gaskets, valve cover gaskets, water pump, water temp sensor, IAC, TPS and now O2's bank 1 and 2, plugs and wires.

This was 2 weeks ago and the O2's to me look like they are doing good, bouncing from like 128-650-ish mV. No more than -/+5% trims


Then 3 days ago the right bank went haywire and the INT counts skyrocketed off the charts when it went closed loop (green on graph) and left bank nose dived but still bounced up and down. Car ran good though except at stops.



Then after changing both O2 sensors, neither one sent any signal, the image below is after 30 minutes of driving. You can see it's still open-loop, stuck at the default 457mV, and still bogged down at stops.

 

I have seen multiple new O2 sensors from some brands be DOA out of the box. I strongly recommend the NGK/NTK brand. You can still probably get those pretty cheap from Rockauto or Amazon. You don't have to any computer wizardry when you swap them. They should just work. The other issue could be the wiring harness to the sensors, of course. But the chance of that failing on both sides of the car at the same time are really tiny.

 

Following with similar O2 failure issues on my 94