Hey everybody,
I think my '93 Z28 has bad O2 sensors, but I would like to run this situation by you first. One sensor was replaced, along the ECM and PROM a few months ago, and things had been going alright until I started throwing trouble codes so my friend has Diacom and the code was O2 Sensor failure on both the left and the right. We have been monitoring the voltage reported and it seems that the voltage stays constant at 451mV exactly (no variation) most of the time, especially when at idle. A possibly related problem is that the car drops RPMs and stutters for a sew seconds at about 400-500rpm when stopping from any significant speed. Could this possibly be related?

My point is basically this. At least one sensor was replaced in about June (a shop did it so I don't know what brand he used) Could both sensors be broken at the same time? Or maybe is there like a sender unit or something that isn't reading properly? Help please!!!

Also, how hard are the sensors to replace yourself? Thanks.

 

Both sensors failing is unlikely, especially one that is only 4 months old.
Changing them yourself is easy and they are not expensive. $32 each for ACDelcos when I bought them two years ago.

 

Ok, now things are about to get complicated I think. I replaced one sensor and still the same thing. No change at all. I am starting to think that there may be a short or a loose wire connection somewhere due to the following new observation: Watching the Diacom readout while driving, the sensors tend not to work (i.e. stay at 451mV exactly) until either I give the car a significant amount of throttle or jostle/brake the car to the right or in various directions. They will then work for a little while (i.e. readings all over the scale as I hear is normal) and then return to 451. So following that line of reasoning, does anyone know where the trace of the wires connecting the O2 sensors goes? Does anyone have any other ideas? I think I may need to inspect these wires and/or run resistance tests. Your help is appreciated.

 

Off-subject, but is your cat clogged? Sure will crap out the idle if it is

 

my car has the same problem but when i drive it and try to give it a lot fo throttle it bogs out bad and feels like it wants to die!!
it has even stalled on me a few times comming to a light or a turn...i havent checked the cat nor the o2 sensors..where are the o2 sensors at?

 

Well funny you mention that, because I have found them both but only one of them is trivial to remove. They are on the Y-pipe, before the 2 pipes meet. The driver side one can easily be reached by lifting the front of the car and basically crawling back until the oil filter is like directly above your head. You will see a wire connecting to a screw in sensor into the Y-pipe. That one was easy to work with which is why I replaced it. I can see the other one from the top of the engine looking down toward the passenger side of the Y-pipe...it looks the same and it isn't very hard to find. Reaching up there is another story, however....hope that helps but I am really looking for assistance with this whole problem. Any information or suggestions are appreciated. Thanks.

 

Well, to be honest, the last time I had the car in the shop the guy over there said the cat was clogged, however, at the time I thought he was just trying to rip me off because I took it for NJ state inspection and it passed the first time. I figured it couldn't be clogged if my exhaust fumes were rated up to par by the state? The condition has changed since then though...the near death at idle has become progressively worse and I have come close to stalling quite a few times, so it's definitely worth a second look. How do I check if it's bad or not?

 

Does anyone have an answer?

 

I have an issue somewhat similar to yours that is driving me nuts. But my problems seem to start after my long tube header install. I was running a program on the laptop which said both 02's are failing. I JUSt replaced them with brand new GM sensors and brand new 02 extension wires from speed inc. I got a new program and OBD1 conversion. I checked all fuses, checked as best I could for exhaust leaks. I have also checked all wiring to see if anything was burnt on the headers which none of them come even close to the headers. I am clueless.
Im looking for help also!!
P.S. so now im running the car in openloop mode so it is not using 02 sensor readings. Car runs great and smoother than ever but my gas mileage is suffering slightly.
HELP

 

Clogged cats can still pas emissions. They just become really restrictive to your exhaust.

 

Spinner,
How do I check if my cat is bad or not? Is there some method of telling for sure?

 

Dude, I'm really not sure...I mean I would understand the fact that one wire might be grounding out somewhere, but both fail at the exact same time...there is never a time where one is working and one isn't...I don't understand!!! I had my ECM and PROM replaced a few months ago for another problem, so I'm fairly sure that it isn't the culprit. I need to find out which wires at the ECM are for the O2 sensors on my 93 so I can do a continuity test with an ohmmeter. Anyone have any info? Thanks much.