I did an idle test/scan tonight in my garage, and was just looking at the data. Looks like it was staying in open loop when i was just idling, then went closed when i hit the throttle up and down. After a few seconds after that, it would go back to open loop. It did this as it was warming up as well. BLM was about 118 during idle and went upto 128 while i was reving it. Ths NB was running around .3-.4 volts, but was bouncing around nicely.

I have the NB O2 sensor in the collector, left side where the bung is when i got the headers. I put my WB right near there in the top of the Y-pipe, less than 6" from the NB location. Do you think the exhaust cools down enough to not let the NB sensor function? I am running a Bosch 1 wire factory replacement unit. I been reading about the heated 3-wire sensors, and I am leaning towards the ACdelco part. Think that would help?

 

are the headers coated? mine are.

i am using same NB bosch you are and i have it directly behind collector in the exhaust pipe. goes CL at about 160-165 CT. my WB is mirror image in opposite pipe. if you are not using a coated header is it possible it is dissapating heat too quickly? my A/F shows lean at startup (WB) and stays lean in CL(BLMs) until the manifold is heat saturated. my OL start upA/F and choke needs some work.

 

on the lean warmup - Just be sure to calibrate O/L idle and such with the Air pump disconnected from the manifolds.

If the ECU sees the O2 voltage within the .35 to .55 volts range, it'll quickly detect that the sensor has cooled down and go open loop. Cooling down or overheating or bad grounding are the only things I've seen make it work and then not work like that (doubt it's overheating, and doubt it's bad grounds). Maybe poisoning or coating could cause a similar reaction.

 

I had to convert to a 3-wire heated AC-Delco O2 sensor to get rid of the same problem you're seeing right now. Heated sensor eliminates exactly what you're seeing!

 

Same here.

 

Bosch NBs have had a known problem for years.......

Get a Delco 3 or 4 wire heated O2 sensor, and you shouldn't have any problems.

 

Slightly off topic fellas, but had a problem with my headers and plumbed an o2 fitting on the pass side collector to run the nb o2. Could I just plumb a fitting into the driver side header to run a wb o2? is there an optimal spot for either? Thanks fellas, new to tuning, so bare with me

Will

 

My headers have the Sterling Silver coating from Jet-Hot, they really run cool. And I dont run the AIR system at all, i kaizaned that junk when I did the header install. My Bosch O2 sensor isnt that old, I put it in about sept of 2003. when the new headers went it.

I have read some old posts about the Bosch sensors, and I been leaning towards the 3-wire heated Delco units. I think that is what my '92 S15 truck runs. Most all new vehicles running heated sensors.

Now where did I put that p/n for the AC unit.......

 

AFS-74 is the delco number of the 3 wire that is recommended by a few on this forum.

 

Thanks for the number, eric. Does Advance Auto sell that unit, or will I be heading to my local GM dealer?

 

I'm certain that they can get it if you ask for it. I know Hi-Lo will

 

I bought an AC-Delco NB from a Chevy Dealer. When I opened it, it had the Bosch logo on it.

 

Last month I purchased an AFS-20 one wire NB O2 from the local Chevy dealer. Has the AC/Delco trademark/logo on it. This sensor is used in a whole lot of vehicles from CCC f-body's, to EFI f-body's, to a host of other GM vehicles.

RBob.

 

You'd due best to sample both sides, ie at where ever both collectors tie together.
Or run dual WBs.

The WBs don't need to be right up by the exhaust ports. As a matter of fact mounting them back some distance, like near where the cat was, is helpful in reducing particulate matter contamination. I've run my behind where the cat was, for years now, without a problem, whereas I've heard of few failing when right up by the engine. If you get too far back, then they're be a little delay in reported AFR changes.

 

FYI: I had the same problem when I first started scanning and was told to get a heated O2. I just bought a new Bosch and put it in. That has worked for a year and a half now. My O2 was just bad and did not know it.

 

Alright, quick question.

I did a search of heated oxygen sensor and three-wire sensor, etc. I have found two ways to connect the 3-wire sensor.

The first one in the list says that all you need to do is connect one wire to ground, one to the ECM, and one to a 12v key in run position hot wire.

The second one has a complete relay system and getting power from the ECM. It also says that the heated part of the sensor will be disabled once the ECM finishes the ground and disables the relay, thus ending the heating cycle.

Which one is correct?

One, which can be found at:
http://sethirdgen.org/HO2S.htm

And the other which is here:
https://www.thirdgen.org/techbb2/sho...=sensor+heater

 

Both will work. The relay system just doesn't heat the NB all the time, only when the ECM thinks it needs more heat. I prefer to just have the heat on whenever the key is on/engine is running so there's no lag while it has to heat up again....

 

I wouldn't say either answer is wrong.

IMHO, the simple answer, "hot in start or run" is just fine. That's how GM does it on the OEM heated sensor apps I've seen. Also, the heater only draws a few mV of current, so there's no need for a separate relay.

If you want to get creative, and spend your time building a more complicated circuit, that's fine too.

 

Cool, just wanted to check.