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Testing Jeep O2, Oxygen sensors

What were your fuel trims?
Did it loop open/closed back and forth on cold start?
Wish I could find a new o2 sensor that didn't have the pre-heating element.

Fuel trims were OK in the beginning, but slowly started to creep high. As it failed, I noted it would open/close on cold but eventually just stuck open.
 
I put in a sensor found on 89 in the junk yard. Out of the three one showed ohms but was not 5-7.

It does not cause a battery draw. But after installing it my A/C clutch started working.

I will do the tests as suggested and post the results.
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Also bought one another on ebay, (hopefully the image of it can be seen), looked identical to my original one. It too caused a parasitic draw. I guess you cant tell by looking at them if they will work or not.
 
I have discovered that there is a diode on the AC clutch power, and two of them on the E-fan feed. Seems there are two paths that can power the Renix e-fans, one comes from the power feed to the AC clutch. That may be a clue to your AC clutch anomalies?

It was interesting to note for me that right at the same time I was getting parasitic draw from the sensors my A/C clutch stopped engaging. Even after removing them.

I bought a bosch and Walker sensors that matched the one I had before all my troubles started, white body, perforations on tip, Hole in the end with a flat bar insided. Both caused parasitic draw.

I got 3 junk yard sensors from 88-89 renix jeeps. No parasitic draw from any of them. 2 of which I got no ohms reading. 3rd one got 3.7 ohms.

After installing the one with the 3.7 ohms reading, no parastic draw and A/C clutch now engages.

While engine is cold loop would switch open/closed, but only till it warmed up, then it stayed on open loop.

Parasitic draw is obviously caused by the sensors having a heating element. Have no idea as to why they affected my A/C clutch.
 
I’m having trouble with my 89 yj starting in cold weather. It will fire but won’t stay running until I’ve cranked it 6 or 8 times and then it’s still very cold natured. I checked the IAT sensor and coolant sensor and they are both good. I replaced the throttle position sensor. I followed the O2 sensor troubleshooting detailed by ecomike earlier in this thread and discovered that I do not have the 5v coming from the ECM to the O2 sensor. Does this mean I have a bad ECM? Where do I go from here?
 
I would suspect damaged wire, or connections first.

Are you testing the correct wire for the 5 Volts?

Are you testing it while connecting to the O2 sensor? If yes, disconnect the O2 sensor and test the ground and the 5 Volt wire from the ECU next.

The if needed test them again at the ECU before declaring the ECU to be the problem. Never heard of a Renix ECU being bad on that 5 volt feed.

But FYI, a normal Renix with everything working right has a no need for a working O2 sensor to start and idle well cold, or hot. Disconnect the sensor and see if it has other issues?

Have you tested and cleaned all the sensor grounds yet????

I’m having trouble with my 89 yj starting in cold weather. It will fire but won’t stay running until I’ve cranked it 6 or 8 times and then it’s still very cold natured. I checked the IAT sensor and coolant sensor and they are both good. I replaced the throttle position sensor. I followed the O2 sensor troubleshooting detailed by ecomike earlier in this thread and discovered that I do not have the 5v coming from the ECM to the O2 sensor. Does this mean I have a bad ECM? Where do I go from here?
 
Poor fuel mileage continues.

Crawled under and ran tests on the wiring. Signal wire shows good swing from .1 to .88 at idle volts I think I saw .9 for a split second. Heater wire shows battery voltage, grounds are under 1 ohm.

IAT and Coolant temp sensors have been tested and found to be in spec.

I'm about to do a smoke test on the intake, vacuum and evap systems and if that doesn't show anything I'll test the MAP sensor guess I'll need to get a hand vacuum pump to really test that?

I guess it could be a no good O2 sensor straight out of the box. I know now the NTK sensors are the preferred ones, I went with a Bosch as I had done in the past before I foudnout about the NTK deal.
 
I would suspect damaged wire, or connections first.

Are you testing the correct wire for the 5 Volts?

Are you testing it while connecting to the O2 sensor? If yes, disconnect the O2 sensor and test the ground and the 5 Volt wire from the ECU next.

The if needed test them again at the ECU before declaring the ECU to be the problem. Never heard of a Renix ECU being bad on that 5 volt feed.

But FYI, a normal Renix with everything working right has a no need for a working O2 sensor to start and idle well cold, or hot. Disconnect the sensor and see if it has other issues?

Have you tested and cleaned all the sensor grounds yet????[/QUOTE

I was testing with the sensor unplugged and was getting 12v supply on one wire, and ground on the black wire which I traced all the way back to the sensor heater where it physically attached to ground but no 5v on the third wire. What other sensor grounds would you be referring to? Unplugging the O2 sensor does not seem to change anything when starting cold. I’ll try to get under the dash and check at the ECM.
 
Unplugging the O2 sensor does not seem to change anything when starting cold. I’ll try to get under the dash and check at the ECM.

That is revealing right there. Obviously an issue with the ECM and or the wire from the ECU to the O2 sensor.

Cold start issue could be many things at this point, but I would solve the 5Volt wire/ECU first and see if the cold start issue is still there or not.
 
IF you have an analog high impedance meter, it should narrow down to a tight range in closed loop at 2500 rpm, like .35 to .55 V with a very tight rapid swing. Any codes? Define poor mpg and any mods....

On HO rigs, I have never heard anything good about any O2 sensors except NTK. Is the exhaust manifold cracked????

Poor fuel mileage continues.

Crawled under and ran tests on the wiring. Signal wire shows good swing from .1 to .88 at idle volts I think I saw .9 for a split second. Heater wire shows battery voltage, grounds are under 1 ohm.

IAT and Coolant temp sensors have been tested and found to be in spec.

I'm about to do a smoke test on the intake, vacuum and evap systems and if that doesn't show anything I'll test the MAP sensor guess I'll need to get a hand vacuum pump to really test that?

I guess it could be a no good O2 sensor straight out of the box. I know now the NTK sensors are the preferred ones, I went with a Bosch as I had done in the past before I foudnout about the NTK deal.
 
IF you have an analog high impedance meter, it should narrow down to a tight range in closed loop at 2500 rpm, like .35 to .55 V with a very tight rapid swing. Any codes? Define poor mpg and any mods....

On HO rigs, I have never heard anything good about any O2 sensors except NTK. Is the exhaust manifold cracked????

13.266MPG overall average (with a 75/25 mix of Highway/City driving) with one outlier of 11.2mpg (on 5th fill up) and one of 16.6mpg (straight highway for a whole tank)

Mods
235 tires
"Upcountry" suspension
2 inch reciever hitches front and rear
No armor or aftermarket bumpers or anything like that

Parts replaced so far,
Full tune up with air filter, plugs, cap, rotor, wires ect
O2 sensor with the aforementioned Bosch
Both CCV Elbows
Sections of nylon vacuum line that had cracks.

Waiting to be replaced,
New STANT t-stat with OEM Mopar TSTAT because I'm getting huge temp swings currently so thinking that STANT may have been bad out of the box

Parts tested and checked good-
Coolant temp (in the thermostat housing)
Intake air temp
Vacuum (pulls 20-21 inches at idle with no fluctuation of the gauge)

Tests waiting to be done due to time
MAP sensor testing
Smoke testing of Vacuum, brake booster and EVAP systems. Doing the propane torch method showed nothing but I still want to do the smoke test.

No codes using the key on-off method of pulling OBD1 codes

I've attached a chart below from the app I use to keep track of mileage, service, ect. This is my 4th XJ and the only one so far that hasn't gotten high teens or even 20mpg on the highway.

0fe82764a5f841bd4d463a86d3842f0f.jpg
 
If it is an OBD-I 1995, no one I know of has ever had any luck with the Bosch O2 sensor. They all say to use the NGK OEM version.

Cracked or leaking exhaust manifold (or gasket) screwing with O2 sensor data

Bad CTS, running to cold to go and stay closed loop

Dizzy timing issues, late spark....

slipping Transmission, no TC lock up.

Too much idle time at fast food lines, LOL. :laugh3:
 
I'll pick up an NGK (or NTK?) O2 sensor they aren't that expensive.

I replaced the exhaust manifold as mentioned in my last post. And used an OEM gasket. No evidence of leak but again I'll be smoke testing it soon. Maybe tomorrow.

CTS Has been checked and based on FSM chart is good to go. I'll be replacing the less than 3 month old stant with an OEM thermostat hopefully today or tomorrow.

I'll double check my ignition timing I replaced the distributor seal a while back with an Oring but pretty sure I put it back in properly since I saw no change in how the Jeep ran or the fuel mileage.

Transmission shows no signs of slippage but passes all testing I can do per the AW4 manual without a pressure gauge.

I idle it long enough to load my gear for work and that's pretty much it.
 
I have seen 16 mpg highway and 10 mpg stop and go (fast food stops LOL) as a common range on mine.

What is/has been the operating engine temps?

Rad feed and outlet temps?

Any power issues? Like a partly blocked Cat?

NTK/NGK seem to be the same company.

The engine can run one tooth of indexing, the ECU compensates, and some 4.0 factory cams on the engines required special dizzy indexing. See Cruiser54's site and specs on indexing for optimum operation. Made a huge difference on mine. Also his use of a custom made window-in-the-dizzy-Cap makes it impossible to screw up the indexing.

Is your engine/ecu stuff all oem 1995?
 
I have seen 16 mpg highway and 10 mpg stop and go (fast food stops LOL) as a common range on mine.

What is/has been the operating engine temps?

Rad feed and outlet temps?

Any power issues? Like a partly blocked Cat?

NTK/NGK seem to be the same company.

The engine can run one tooth of indexing, the ECU compensates, and some 4.0 factory cams on the engines required special dizzy indexing. See Cruiser54's site and specs on indexing for optimum operation. Made a huge difference on mine. Also his use of a custom made window-in-the-dizzy-Cap makes it impossible to screw up the indexing.

Is your engine/ecu stuff all oem 1995?

On a 50 mile commute with only 14 of that being county road and city street (10 miles of easy county road with one stop sign qnd 4 miles of city streets) i would expect to be a lot closer to 16MPG than i am now.

See the picture below for temp swing to and from work. This is reading with a new OEM temp sender in the head. This seems to be pretty accurate based on IR temp gun readings.

No power issues. Vacuum test done to test for exhaust blockage and was negative.

As far as i know its all stock. No chips or anything visible.

47f44d7f1f86f9092dafceff0f7c8378.jpg


Sent from my SM-G892A using Tapatalk
 
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If it is an OBD-I 1995, no one I know of has ever had any luck with the Bosch O2 sensor. They all say to use the NGK OEM version.

Interesting. I've had what I believe to be a Bosch O2 sensor in my '92 for a few years now, I'd never heard that bit about the Bosch not working well.

I'm only getting about 12-13mpg, but I'm pushing 31x10.50 MTRs with stock 3.55 gears, so figured that was the issue (did change speedo gear to correct for tires/ratio, so know speedo/odo is right).

May have to investigate this...
 
I've run basically every reputable brand of O2 sensor and never had an issue with any of them...
 
I have had similar results with a variety of spark plugs, but did find the NGK plug (on a Renix) to be just a wee bit hotter, hotter enough to not oil foul on 2 of 6 cylinders I had started having problems with. Before that, I had been using a Bosch platinum every one here said would not work. So who knows, LOL. But there has a been a rash of recent reported issues with the Renix Bosch O2 sensors the last 6 months. I have never used anything but Bosch on my Renix, and all mine are Renix.

I've run basically every reputable brand of O2 sensor and never had an issue with any of them...
 
That is revealing right there. Obviously an issue with the ECM and or the wire from the ECU to the O2 sensor.

Cold start issue could be many things at this point, but I would solve the 5Volt wire/ECU first and see if the cold start issue is still there or not.

So I finally had a chance to do some more troubleshooting. I located the 5v wire coming out of the ECM and verified that I’m not getting the 5v out of the ECM. Sometimes it will read .2v but never anything more than that. Is this an ECM problem then and if so where do I get one?
 
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