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  #91  
Old January 15th, 2014, 10:30
blistovmhz blistovmhz is offline
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Re: Testing Jeep O2, Oxygen sensors

Quote:
Originally Posted by Ecomike View Post
I think the exhaust dent is factory.... Did you replace the donut seal and make sure the threads were good, and that you got a good seal at the flange?
Okay, so I took off the downpipe to "fix" that dent and the next day I had to go do my vehicle emissions test. Failed miserably with extremely high NOx and slightly high HC/HO.

Back in the garage, I replaced both O2 sensors, made sure my exhaust was sealed, and somehow decided I thought I had a leak between my #6 cylinder and the rear water jacket, so I pulled the head, cleaned up the chamber/valves/everything, threw in a new head gasket, and while I was at it I threw on my new exhaust header and new RAD.

Some time between fixing the exhaust dent, and doing everything else, MPG and power dropped by around 20-30%. The cylinder leak seemed to be real as I was blowing exhaust into the rad. Not doing it anymore, so I figure I wasn't wrong.

I checked the O2 with an analog multimeter, but the only one I can find has minimum increments of 5V and it's really difficult to see if it's flapping around correctly. According to my OBDii interface, the upstream O2 isn't flapping very often, and that's what it looked like on the multimeter as well. Swapped back my old O2 sensor and get the same response. Tried a third just cause, and same deal.

So, assuming I'm reading the O2 correctly, what would cause it to have a slow response? Vac leak might do this? Or as a few guys have hinted at before, maybe hammering out that exhaust dent really did cool down the exhaust stream and now my O2 isn't working properly? Or, as you suggested, maybe an exhaust leak? (it'd have to be a pinhole cause I can't find it.)
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  #92  
Old January 15th, 2014, 21:17
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Re: Testing Jeep O2, Oxygen sensors

If the 98 has precats in front of the front O2 sensors they may have been damaged some if coolant got to them.

Check the HEGO fuse, that powers the heaters again in the O2 sensors.

The analog meter must be at least 20,000 ohm impedance or the meter screws up the reading, and the sensor must connected to the PCM/wiring, so you must back probe the connect with a good probe-contact to get good reliable readings.

Sounds like the engine was running too lean, which could have damaged the rear cat converters. Does the engine bog down on acceleration or high rpms?

I am not the expert here on the 98s, so maybe others will post up. Might also check for damaged wires to the O2 sensor, road hazard, contact with hot parts could have damaged the sensor wires to the PCM
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  #93  
Old January 15th, 2014, 21:28
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kastein kastein is offline
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Re: Testing Jeep O2, Oxygen sensors

Ecomike is probably on the right track, but I just want to clarify that 98s don't have precats. Only 01s and CA emissions spec 00s have them.

Also, I am 99% sure that on HO XJs/MJs, the same fuse (it's a blue 15 amp one, iirc) powers the ECU, both O2 heaters, the alt field coil, all the injectors, the fuel pump, and the ignition coil. Because for a while I had a wiring issue on my 96 (shorting out downstream O2 heater wire) that would blow that fuse and leave me dead in the water, and my 98 did the same exact thing when the fuel pump wiring got shorted as well as when the O2 wiring got smashed a few years back. I'm not 100% on that exact list of things powered by that fuse, but it's definitely accurate with regards to the ECU, O2 heaters, and fuel pump, because they sure shut it off in a hurry when the O2 heaters/fuel pump wiring shorted out
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  #94  
Old October 7th, 2014, 02:31
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photondisruptor photondisruptor is offline
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Re: Testing Jeep O2, Oxygen sensors

I just diagnosed a faulty sensor on my 1990 Renix with a 3-pin weatherpack adapter I made. It's basically about 6" of wire with male and female connectors on either side, and extra leads about 2' long crimped in for a good secure connection.

I hooked up my DMM and measured the sensor heater resistance at 50kOhm (dead). I then hooked it to the ECU and measured about 14V from the heater relay, and 5V from the ECU.

When I started up the engine, nothing changed, it ran rough, and the sensor indicated a solid 5V "signal".

I popped in a brand new Bosch 12009 and repeated the tests, and the heater voltage dropped to about 12.5, which meant it was actually working. The sensor voltage provided a solid tick-tock after only about 8 seconds of warming up.

I made this video to show what it looks like on my DMM:
https://www.youtube.com/watch?v=OchhM-F5UiM
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  #95  
Old April 10th, 2016, 13:42
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Re: Testing Jeep O2, Oxygen sensors

Nice update to my old thread. Just found it, thanks. I was ill and off line most of that year. Be cool if someone did a youtube renix analog meter testing how to story some day. You tube has saved me some much time the last year working on the Ford and the Saturn...and doing my first ball joints this year on an XJ. Many people seem to follow how tos better with video. I do better with text in most cases, but video does show the exact parts and locations etc.

Quote:
Originally Posted by photondisruptor View Post
I just diagnosed a faulty sensor on my 1990 Renix with a 3-pin weatherpack adapter I made. It's basically about 6" of wire with male and female connectors on either side, and extra leads about 2' long crimped in for a good secure connection.

I hooked up my DMM and measured the sensor heater resistance at 50kOhm (dead). I then hooked it to the ECU and measured about 14V from the heater relay, and 5V from the ECU.

When I started up the engine, nothing changed, it ran rough, and the sensor indicated a solid 5V "signal".

I popped in a brand new Bosch 12009 and repeated the tests, and the heater voltage dropped to about 12.5, which meant it was actually working. The sensor voltage provided a solid tick-tock after only about 8 seconds of warming up.

I made this video to show what it looks like on my DMM:
https://www.youtube.com/watch?v=OchhM-F5UiM
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  #96  
Old April 27th, 2016, 13:59
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Re: Testing Jeep O2, Oxygen sensors

How interesting and bizarre, Crazy that by the HO period they would shove all of those on one fuse, sounds more like an AMC save pennies standard than a more modern Chrysler standard. My 2001 Saturn has 2 ECU/PCM fuses in two locations (dash and under the hood as I recall, a PCM-A and a PCM-B) just for the PCM.

On the 87 Wagoneer XJ I have, the only facotory fuse on the O2 heater power is a huge fuse link near the battery that I smoked in the middle of no where one day when it got too close the exhaust manifold (my prior friend-mechanic routed it wrong when he installed the new one ages ago). My voltage dropped way deep into the red, AC died, and finally smoked from under the hood. I pulled the O2 heater relay that was still working and drove the last 200 miles home with no problems.

Quote:
Originally Posted by kastein View Post
Ecomike is probably on the right track, but I just want to clarify that 98s don't have precats. Only 01s and CA emissions spec 00s have them.

Also, I am 99% sure that on HO XJs/MJs, the same fuse (it's a blue 15 amp one, iirc) powers the ECU, both O2 heaters, the alt field coil, all the injectors, the fuel pump, and the ignition coil. Because for a while I had a wiring issue on my 96 (shorting out downstream O2 heater wire) that would blow that fuse and leave me dead in the water, and my 98 did the same exact thing when the fuel pump wiring got shorted as well as when the O2 wiring got smashed a few years back. I'm not 100% on that exact list of things powered by that fuse, but it's definitely accurate with regards to the ECU, O2 heaters, and fuel pump, because they sure shut it off in a hurry when the O2 heaters/fuel pump wiring shorted out
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Quote=8Mud: "Go ahead and put up the best fence you can build, I'll bet on some Mexican with a few dollars of nails and a pile of scrap lumber."
34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091
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  #97  
Old June 11th, 2017, 16:20
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Ecomike Ecomike is offline
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Re: Testing Jeep O2, Oxygen sensors

I am revisiting this subject as my Renix rig is switching from closed loop to open when It stumbles in a miss fire I am troubleshooting. When it goes to and parks in open loop for 1-2 minutes at idle before finally going back to closed loop, my Snap-on MT-2500 reads about 0.68 Volts, low volts, and claims the engine is running lean.

But one of my last posts here seems to contradict this, and to make matters worse, the Snap-on MT-2500 manual says the opposite of what the scanner says, LOL, it says low volts is rich???. Whose on first and whats on second.

HTh do we nail this down once and for all???



Quote:
Originally Posted by Ecomike View Post
Read it again, the patent says that Wiki is right and the FSM is wrong (if in fact the FSM is reversed?).

One thing you missed, to add to the confusion, is that if the engine is running rich due to a leaking fuel injector (say on one cylinder) or FPR, the ECU may be fighting the leak by trying to run the rest of the engine lean, and if there is an exhaust manifold leak near the O2 sensor, all bets are off as to what the O2 sensor reading really means!!!

I am pretty sure (IIRC) that a high voltage O2 sensor reading on renix, is a rich, excess fuel reading. I will try and dig up my old notes later when I get time, but reread the bottom text of your patent post, it says high voltage is rich, excess fuel.
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34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091

Last edited by Ecomike; June 11th, 2017 at 16:23.
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  #98  
Old June 11th, 2017, 17:08
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Re: Testing Jeep O2, Oxygen sensors RENIX Manual is right

Is it possible that the Renix O2 sensor high voltage, 5V versus low voltage down to 0.x volts lean/rich is the opposite from the HO 0-1 volt sensors?

And that is what has caused much of the manual confusion over the years?

Am no longer sure which is right for Renix. My Snap-on MT-2500 says low voltage on Renix is LEAN, but the manual that comes with it says low voltage on Renix is rich. Mine is running low voltage in open loop which should be rich unless something is wrong, and mine has a miss when I give it gas, so something is wrong, but at idle for 1-2 minutes it goes back to closed loop, so the O2 sensor works. I am tracking down injector, or cylinder or plug issues causing the stumble on revving.

Quote:
Originally Posted by nickguy View Post
It has been mentioned in other threads that the RENIX version how o2 content is measured is a little different than you would expect. It is pretty confusing and totally counter-intuitive.

From the RENIX manual

"When the oxygen content is low, (rich mixture), the voltage signal will be less than 2.5 volts. A lean mixture (high oxygen content) the voltage is signal is above 2.5 volts."

So
1 volt = rich
5 volts = lean
2.5 just right....

(more o2= lean mixture = lower resistance = higher voltage ???)

From wikipedia which quotes other references so it must be true.

"So, for fuel-rich exhaust (lower oxygen concentration) the resistance is low, and for fuel-lean exhaust (higher oxygen concentration) the resistance is high."

(more o2= lean mixture = higher resistance = lower voltage )


Another reference

http://www.hybridconversions.com/v/v...0explained.pdf

As titania is an N-type semiconductor with a structure TiO2-x, the x defects in the crystal lattice conduct the charge. So, for fuel-rich exhaust the resistance is low, and for fuel-lean exhaust the resistance is high.
(more o2= lean mixture = more resistance = lower voltage) same language that wikipedia uses)

(more o2= lean mixture = higher resistance = lower voltage )

Anyway I spent some time on this today and I think I can confirm that the RENIX ECU will see high voltage as rich and low as lean. I had a bad fuel pressure regulator and it caused the o2 sensor to read less than 1 volt consistently at idle. This drove me crazy and I am hoping this research helps others that are struggling with the same troubleshooting dilemma. If you have a RENIX sensor that consistently reads less than 1 v after warmup something is causing it to run rich and it is likely to be the fuel pressure regulator. It means the o2 sensor is functioning properly.

Think that this is confusing because you have multiple reverse logic things happening.

Higher resistance = lower voltage higher o2= less resistance = higher voltage... arghh!!!


So I smelled a rat and decided to read the bloody patent. Which I have linked to and list the relevant excerpt below. It would appear that Titania sensor's resistance actually decreases with the amount of o2 in the stream. It is an inverse relationship....

(more o2= lean mixture = lower resistance = higher voltage )

I am going to challenge Wikipedia on this unless anyone sees what I am sure I am missing.


http://www.google.com/patents?id=pFI...1792 &f=false





Done.
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  #99  
Old April 7th, 2018, 01:45
randy57 randy57 is offline
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Re: Testing Jeep O2, Oxygen sensors

1990 jeep renix.

Replaced o2 sensor.

Voltage bounce from .14v -.16v.

Stays in closed loop even after reaching opperating tempature.

Ignition off o2 causes parasitic draw. Relay works fine.
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  #100  
Old April 7th, 2018, 01:50
randy57 randy57 is offline
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Re: Testing Jeep O2, Oxygen sensors

Correction: Stays in open loop not closed.

1990 jeep renix.

Replaced o2 sensor.

Voltage bounce from .14v -.16v.

Stays in closed loop even after reaching opperating tempature.

Ignition off o2 causes parasitic draw. Relay works fine.
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  #101  
Old April 7th, 2018, 17:42
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Re: Testing Jeep O2, Oxygen sensors

"Ignition off o2 causes parasitic draw."

Can you explain? the O2 sensor is two resistors. one is a heater, the other a temp-variable resistor.

Parasitic draw? What and how are you testing????

Are the harness wires damaged????
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  #102  
Old April 8th, 2018, 22:10
randy57 randy57 is offline
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Re: Testing Jeep O2, Oxygen sensors

Cannot explain o2 sensor resistors. All I know is that my battery was dead due to new o2 sensors. Never had dead battery before replacing o2 sensor so I assume the wire harness is fine.

Testing why battery was dead.

Battery is new, must be a parasitic draw on battery. Disconnect battery negative, key off, nothing on. Put volt meter on 10 amp setting, touch one lead to battery negative, other lead to battery negative terminal and read amps.

Almost 2 amp draw slowly dropping to .86 amps. Unplug o2 sensor and read voltmeter, 0.0 amp reading.

I tried a NTK from Pepboys. Was supposed to have been a direct replacement but looked nothing like the original I had, it caused a parasitic draw.

Also tried a Bosch from O'reilly's. Was also supposed to have been a direct replacement and it looked nothing like the original either, it too caused a parasitic draw.

Never had dead battery before replacing o2 sensor.

Why did I replace o2 sensor?

Going freeway speed engine stumbles. Get off freeway and drive city speed, engine stumbles and quits. Restart engine, pull over and sit 15 minutes. Begin driving, after 5 minutes engine stumbles. Pull over for another 15 minutes and begin driving, 5 minutes later engine stumble. Repeat this process over and over again till I get home.

I replace IAC and CPS. Take for drive and after getting warm engine stumbles. Replace o2 sensor. Take for another test drive, runs fine. Turn engine off, next day battery dead.
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  #103  
Old April 9th, 2018, 09:38
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Re: Testing Jeep O2, Oxygen sensors

Randy, 99% sure the O2 sensor relay that powers the electric heater element in the sensor is stuck ON, and draining the battery. Change that replay and see if the power draw does not vanish. My compliments on your post, great detail of the story, made it easy to know what is wrong! Not sure if that image below is right, so check some others online or the FSM for the right location.
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  #104  
Old April 9th, 2018, 09:49
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kastein kastein is offline
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Re: Testing Jeep O2, Oxygen sensors

I would agree with Ecomike on this one.
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  #105  
Old April 9th, 2018, 12:12
randy57 randy57 is offline
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Re: Testing Jeep O2, Oxygen sensors

Thanks all for caring enough to give your valuable input. I appreciate it more than you can know.

The image posted for the jeep relays is correct per the FSM for 90 jeep. I replaced the relay and still get the battery draw.

To give you more info on the o2 sensor I have currently, which is also parasitic.

Upon trying the part store sensors (NTK and Bosch), I connected my MT2500 and they both showed a constant 4.98v output. The current sensor I have now, which is an Autolit sensor, the voltage bounces from 0.14v - 0.16v

The Autolite sensor that I have now, because the part stores sensors drained my battery, I bought on ebay because it looked like my original sensor. (ceramic with black boot on end and holes in the end that went into the exhaust). That sensor is new, it was just an older part from either a parts store or a repair shop that went out of business. And looks like it is in perfect condition.

The ebay listing showed it to be Autolite 02024 Oxygen O2 Sensor For 1987-1990 Jeep Cherokee, wrangler, Comanche. The only difference was that the connector on the autolite was a (male), connector. Wires were Grey, black and yellow. Where as my original sensor had female connector with grey, black red wires.

Looking at the 87-90 cherokee FSM, it showed that the Autolite ebay sensor was for the 2.5 liter with the yellow wire going to ignition and the grey wire going to ECU and black to ground.

Where as the FSM showed my original 4.0 sensor as having the grey to ECU, red to relay and black to ground.

Because the ebay autolite had a male plug, I replaced the it with the female plug from my original sensor. Grey to grey, black to black and red to yellow. ( I soldered the connections).

Is it possible that the o2 sensor for the 2.5 liter behaves differently than the 4.0 liter sensor?
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