I have a 97 TJ 4.0 With aftermarket headers and a cat delete. I am having O2 sensor issues due to this. Has anyone used the heated 3-5 volt 4 wire 02 simulator from Magnum Tuning for their upstream sensor?
O2 Sensor Simulators
- Thread starter jeansnjameson
- Start date
The down stream is the only one that reads differently without the cat. it's sole purpose is to tell the computer if the cat is working properly or not. The upstream sensor monitors lean/rich conditions, which you don't want to get rid of.
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Wow looked up that HP tuners $400. Anything under $200 that could do that? I am also looking to remove my cat this summer.
The '97 2.5 I had, plugged the cat twice in less than 50k miles, the first time it was under warranty. The second time we took the muffler off and used a steel bar to brake apart and gut the cat (while on a wheeling trip) then reinstalled the muffler, it never set an O2 sensor code. Not sure why but it might be worth the effort to see if you can get the same result without spending any $$
It's been so long since I had the '97 it's hard to say. I don't honestly remember it changing fuel economy very much at all but then again I didn't pay much attention to fuel economy 23 years ago.
I did notice a slight improvement driving down the interstate above 55 I didn't have to shift down to 4th quite as much on some inclines. I was living in the Puget Sound area at the time.
Are you using NTK/NGK O2 sensors?
Edit: one other question, which "97" version do you have? Early and late '97 models are different.
Turdworlder
TJ Enthusiast
Mine has no 2 precats from factory. On vin code history it seems like the very first owner had special tj for export order. It has all the lixuries like cruise control, ac etc but no precats and o2s. Only one o2, cat near transmission. Want to remove it.
Even if it doesn't have pre-cats it still needs to have upstream sensors. The downstream (or after cat) sensor(s) are strictly to monitor the efficiency of the cat. The upstream sensors are what contribute data for fuel mixture adjustments.
Are you sure it’s the upstream O2s you are having trouble with? They don’t care if the CAT is there, the upstream is used by the PCM to calibrate in closed loop. The rear/downstream O2s are the ones that detect if a CAT is present/functioning.
@Jerry Bransford The only thing I believe may be slightly different is I believe Jerry said some years of TJs use both up and downstream O2s to aid in PCM calibration. Which if true, is abnormal.
Can you confirm and say what year Jerry? I haven’t yet started playing with HPtuners on my jeep yet (also abnormal lol)
@Jerry Bransford The only thing I believe may be slightly different is I believe Jerry said some years of TJs use both up and downstream O2s to aid in PCM calibration. Which if true, is abnormal.
Can you confirm and say what year Jerry? I haven’t yet started playing with HPtuners on my jeep yet (also abnormal lol)
Yeah early TJs only had one catalytic converter so there's just one upstream and one more downstream O2 Sensor. In those with the single cat, only the upstream O2 sensor is used to set the fuel mixture. The downstream cat only monitors the sole catalytic converter for proper operation.
For newer TJs with 3 cats, there are two smaller pre-catalytic converters and one main catalytic converter. There are four O2 sensors that go on top of and below the two catalytic converters. I haven't read up much on those but apparently all four of those are used by the PCM to set the fuel mixture.
Interestingly enough, the downstream sensor on the early models apparently only monitors when the converter goes bad. Years ago I had to replace my converter and the downstream O2 alerted me of its poor performance. Fast forward to present day, I've had the CAT removed on my '98 for a while now - no CEL on the dash...
X2. that's what I said in the last sentence in my first paragraph.Interestingly enough, the downstream sensor on the early models apparently only monitors when the converter goes bad. Years ago I had to replace my converter and the downstream O2 alerted me of its poor performance. Fast forward to present day, I've had the CAT removed on my '98 for a while now - no CEL on the dash...
Yessir. I find it odd though that CAT DELETED qualifies as "proper operation."X2. that's what I said in the last sentence in my first paragraph.
Fixed it for ya, and yes I already stated that.
In a different thread on the subject of O2 functionality this information was discussed at length and I don't remember exactly what was said as to whether or not they were indeed necessary, but IIRC they are not 100% vital to the drivability, that they can be programmed out of the system if you wanted to delete the cats, "for off road use only of course". (Added the last bit for legality reasons)
Same result with my '97 4 popper.Interestingly enough, the downstream sensor on the early models apparently only monitors when the converter goes bad. Years ago I had to replace my converter and the downstream O2 alerted me of its poor performance. Fast forward to present day, I've had the CAT removed on my '98 for a while now - no CEL on the dash...
