CAFE Emissions O2's

[SouthSeaPirate]

I have an 01 that I replaced the engine with a 98 ZJ.
With the swap I did a speed daddy header.
IIRC, I should have 5 total O2 sensors.
At this time, I have two in the header.
My questions are;
Which of them adjust the fuel ratio?
How do I tell which is which?
Where should all the harnesses come from?
Mine only had two when I got the Jeep and want to make sure Im not loosing out on power or a whole lot of fuel.
TIA

 

[Saudade]

If you're CA Emissions, you should have 4. Two before the cats, and 2 after. The ones before adjust fuel, the ones after determine cat efficiency.

Bank 1 Sensor 1 (front, upstream) should have a Black/Dark Green wire for the sensor signal.
Bank 1 Sensor 2 (front downstream) should be Tan/White.
Bank 2 Sensor 1 (rear upstream) should be Light Green/Red
Bank 2 Sensor 2 (rear downstream) should be Tan.

 

[Black1990jeep]

If you're CA Emissions, you should have 4. Two before the cats, and 2 after. The ones before adjust fuel, the ones after determine cat efficiency.

Bank 1 Sensor 1 (front, upstream) should have a Black/Dark Green wire for the sensor signal.
Bank 1 Sensor 2 (front downstream) should be Tan/White.
Bank 2 Sensor 1 (rear upstream) should be Light Green/Red
Bank 2 Sensor 2 (rear downstream) should be Tan.

note california 2001s have 3 cats, I believe the free state 2001s had one cat only.

 

[Black1990jeep]

If your 2001 had only two sensors, it was likely a free state jeep, with one cat and two upstream sensors I think thus..... One sensor for front 3 cylinders, one sensor for rear 3 cylinders. Both are used to adjust fuel flow I believe. The one cat will be under the floor. No cat in engine bay.

 

[IslanderOffRoad]

note california 2001s have 3 cats, I believe the free state 2001s had one cat only.

All 2001s have 3 cats. 2000 was the last year for a different 49 state version

 

[Black1990jeep]

All 2001s have 3 cats. 2000 was the last year for a different 49 state version

If that is the case ( and I am not doubting you, cause I dont know for sure either way ) he either dont have a real 2001 US market XJ, or someone cut out or hid away part of the harness containing 2 of the 4 sensor connectors, or there is some other unusual circumstance here.

Now one other explanation is that that free state 2001s, only have two pre catalyst sensors? the two down stream sensors in the four sensor do nothing but monitor performance of the cats and primary sensors so as to give an engine code. This code thing just might have been a California thing only back in 2001? Thus free state 2001s might have 3 cats but only 2 sensors? Just a guess???

Someone with a 2001 factory manual can probably verify these things, and show locations of connectors, wire colors, etc... if they are supposed to exist. That someone is not me.

 

[Saudade]

The OP posted this is other forums and there seems to be a bit of confusion. I assumed when he said 2 in the header he meant 2 in the exhaust manifold, one for each bank. A few pics on the web of the speed daddy headers doesn't reveal much.

Here's an example of Rusty's Off road headers for the 2001 XJ. Note the O2 bungs next to the flanges.

Here's a stock 2001 exhaust with downtube and 4 O2 sensors.

 

[SouthSeaPirate]

Thanks everyone and yes I need to clarify.
It does seem mine should come with 5 O2 sensors, but it also only had wires for two in the header.

So, Im looking to see if post-pre-cat O2s adjust fuel ratio or simply look at cat efficiency. I have harnesses for only two sensors so Im also looking to see how I can possibly know which ones are correct. IE if I only have two now, how can I tell If I even have the right ones connected? And if I can get back to four, where should said harnesses be? Clearly I have to rewire something.

 

[Black1990jeep]

Thanks everyone and yes I need to clarify.
It does seem mine should come with 5 O2 sensors, but it also only had wires for two in the header.

So, Im looking to see if post-pre-cat O2s adjust fuel ratio or simply look at cat efficiency. I have harnesses for only two sensors so Im also looking to see how I can possibly know which ones are correct. IE if I only have two now, how can I tell If I even have the right ones connected? And if I can get back to four, where should said harnesses be? Clearly I have to rewire something.

The electrical or engine electrical system diagrams in the factory service manual are what you need, the should indicate wire locations, wire colors.

You may also gain knowledge on this with an obd scan tool to tell if the ecu is sending an error code. the code should indicate which O2 sensors might be inoperative. If code reader indicates down stream O2 sensors are both bad, but upstream are good, then that leads me to think you two sensors are up stream ones

 

[SouthSeaPirate]

The electrical or engine electrical system diagrams in the factory service manual are what you need, the should indicate wire locations, wire colors.

You may also gain knowledge on this with an obd scan tool to tell if the ecu is sending an error code. the code should indicate which O2 sensors might be inoperative. If code reader indicates down stream O2 sensors are both bad, but upstream are good, then that leads me to think you two sensors are up stream ones

I cant believe I didnt even think about that.
Great idea!

 

[SouthSeaPirate]

Here's how it is setup atm

 

[maxbraketorque]

Those O2 sensors really should be in the collector region. In their current location, they will only key off one cylinder each which is generally undesirable. An average of multiple cylinders (i.e., in the collector) allows the sensors to provide AFR feedback from multiple cylinders which is more desirable for controlling the fuel trims and also for being able to detect problematic conditions. Since that is a 6-into-1 setup, I'd put both O2 sensors just after the collector near the flange.

 

[Black1990jeep]

Those O2 sensors really should be in the collector region. In their current location, they will only key off one cylinder each which is generally undesirable. An average of multiple cylinders (i.e., in the collector) allows the sensors to provide AFR feedback from multiple cylinders which is more desirable for controlling the fuel trims and also for being able to detect problematic conditions. Since that is a 6-into-1 setup, I'd put both O2 sensors just after the collector near the flange.

It is a mixed bag, sure average readings are nice, but the engine brain cant tell which cylinder might be wonky if the sensors average the exhaust gas reading from two or more cylinders. fuel adjustment that an average sensor causes will be based on the average, one bad cylinder has excess O2, so the engine brain enriches all of them, Not ideal either.

The best case is to monitor each cylinder, and individually adjust the fuel to each cylinder. But Id hate to replace that many sensors $$$.

as it is with the system pictured, two cylinders are monitored, four are not. If an unmonitored cylinder has too much O2 (say from a dead spark or clogged injector) the other five cylinders will continue on with correct mixture. if however the monitored cylinder goes bad, too much O2, then the brain will enrich all of them, even the ones that are running correctly, so now every cylinder in that bank will be running bad, one with the fault, the others over compensated.

heck now days you can put not only an O2 sensor on each cylinder, but even a knock sensor on each, and individually control the advance on each cylinder!
Crazy!:bunny:

 

[maxbraketorque]

Yeah, the pros and cons are pretty nearly equally weighted. I like getting a contribution from all cylinders because it has the potential to provide info on cylinder condition before an issue gets really bad. Depends a bit on how routinely the ECU is data logged. I pretty much always have data logging running.

Per cylinder AFR monitoring would be awesome, but as you say, its $$$.