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oxygen sensors and or a pcm reflash?.....

unplug it?
 
I have the same EXACT issue you have. Only my issue started when the O2 wires were ripped out or cut by something. After splicing in a new downstream O2 sensor, and replacing the upstream sensor, I have yeilded nothing. I have the FSM for my 1998 Cherokee, in which I looked over and checked every single circut related to the O2 sensors, and other things which may effect the O2 sensor readings. So then out of curiousity to see if it would change my readings at all, we took the cat out, of course nothing changed.

The sensors on a cherokee are supplied 5v, and then from there they send a reading anywhere between .01v to 1v. Mine send 4.96v back to the PCM. I have had two chrylser guys look at it and they have no idea what could cause the problem. We went through and tested the wires leading to the sensor, the sensor itself and the wires leading back to the PCM, we have found no issues.

So with that, your not the only person with the problem. I'm with you, a carb swap doesn't sound like a bad idea.

Anyways, feel free to contact me, I can get alittle more indepth as far as testing things as well. And if you find a solution definitely let me know!
 
moparjim1987 said:
how do you electronically disconnect the o2 sensor? i work at a dodge dealership so i actually have the tools to fix the thing, just need to know what to do.
Click to expand...

Just disconnect the quick connect conection at the harness / sensor interface.

I cut mine up above in a more accesable location in the wiring harness and installed push pull connectors for easier access and testing.
 
Flammable said:
I have the same EXACT issue you have. Only my issue started when the O2 wires were ripped out or cut by something. After splicing in a new downstream O2 sensor, and replacing the upstream sensor, I have yeilded nothing. I have the FSM for my 1998 Cherokee, in which I looked over and checked every single circut related to the O2 sensors, and other things which may effect the O2 sensor readings. So then out of curiousity to see if it would change my readings at all, we took the cat out, of course nothing changed.

The sensors on a cherokee are supplied 5v, and then from there they send a reading anywhere between .01v to 1v. Mine send 4.96v back to the PCM. I have had two chrylser guys look at it and they have no idea what could cause the problem. We went through and tested the wires leading to the sensor, the sensor itself and the wires leading back to the PCM, we have found no issues.

So with that, your not the only person with the problem. I'm with you, a carb swap doesn't sound like a bad idea.

Anyways, feel free to contact me, I can get alittle more indepth as far as testing things as well. And if you find a solution definitely let me know!
Click to expand...
I need to correct you on a few things. Not sure what year your jeep is you are refering to, but 87-90 Renix Jeeps had a special O2 sensor that is a variable resistor. The ECU feeds it 5 volts to the sensor and compares the return voltage 0-5 volts to a reference resistor in the ECU.

The 1991 and newer models have an O2 sensor that generate their own voltage, which runs between 0-1 volt.

If yours is a 91 or newer and it is being feed 5 volts to the sesnor itself you have something very odd and wrong with yours.

All of them 87-02 have a ground wire, a return signal wire to the ECU, and a 12-14 volt supply wire that supplies power to an internal heater that keeps the O2 sensor at the proper temperature for it work correctly. IF it is not getting 12-14 volts to the O2 sensor heater, or if the ground is bad, it will send out bad, incorrect O2 data.

I believe that both generations of O2 sensors are read by the ECU on the hot wire only with the ECU / PCM using it's own internal ground reference, so the O2 sensor ground is acting as the ground for the the heater and the sensor both, and is not used directly by the ECU, but... or, therefore if the ground wire at the O2 sensor is higher than about 1 ohm to the battery negative post (ohms read with power OFF!), that is one of your problems as a poor ground affects the electron flow through the sensor and causes a back voltage build up in the sensor itself and sensor wire read by the ECU or PCM.

An intermittent short in the wire harness of the O2 sensor wires could cause your problems too.

So, in sumarry, I disconnect my O2 sensor and test the ground wire to the battery in the harness side. Then power on, I test for 5 volts and 12 volts in the other 2 harness wires for 87-90 models, and just 12 volts in one of these wires, and 0 volts in the other two wires for 91-02 models, all with the sensor disconnected.

Then live testing to see if the 0-5 volts (87-90) is oscilating reading between the ground and ECU supply wire across the working (engine running) O2 sensor, or 0-1 volts on the 91-02 models. Either should read 13-14 volts engine running between ground and the Heater voltage supply sire.

Note that the third wire suppplying 12-14 volts to the internal O2 sensor heater is usually larger gauge wire than the other two wires, and is orange on the Renix years.

Lastly, you need an analog display multi meter (volt - ohms) to read live O2 sensor voltages properly.
 
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I have a feeling its not an O2 sensor problem, the PCM doesnt even read the O2s at startup because its in open loop until the engine warms up. Plus the fact that you replaced the O2 and it still has the same problem. I would start looking elsewhere
 
igotanxj said:
I have a feeling its not an O2 sensor problem, the PCM doesnt even read the O2s at startup because its in open loop until the engine warms up. Plus the fact that you replaced the O2 and it still has the same problem. I would start looking elsewhere
Click to expand...

Contrary to some rummors..... they switch into closed loop mode in less than 10 to 15 seconds (30 at the most) for most vehicles and all jeeps since 1987. The built in O2 sensor heater gets the O2 sensor into proper temperature range very quickly, regardless of the engine temperature, and the PCM or ECU starts running in closed loop very quickly, unless the voltage to the O2 sensor heater is not there (busted wire or bad relay or bad PCM wire to the relay or bad PCM) or if the O2 sensor is damaged.

The OP fixed his problem for a while the first time with a new O2 sensor! He also got a bad O2 sensor heater code shortly after installing the second O2 sensor.
 
well, i know one thing for sure, it doesn't have a bad cam lobe or lifter the thing runs too good after the initial hiccup/cough/sputtering thing takes its turn, all i would like to do is figure out what the hell is going on so when i build my new stroker, it doesn't get trashed because of the whole engine electrical system is being a bitch!! thats all.......
 
I'm in the same boat, 99XJ, and I have an aftermarket header.

I'll be replacing TPS and let you know if that helps.

What kind of heat shield wrap do you use, all around the injector, or the wires too??

I'm gonna replace with dealer O2 sensor to see what happens....I am pulling an O2 code with a new bosch "universal" O2 sensor. Wish I didn't spend money on the universal!!!


I've noticed that it's much worse, or maybe just more pronounced on the trail. Maybe it is the heat soak doing it?? It could just be that on the road I just hit the gas and rev it up and past the RPM/throttle position at which it likes to happen real quickly and in 4lo that RPM/throttle position is where it needs to be a whole lot (4.88 gears, etc.) It didn't notice it as much in winter wheeling, although that's kinda a totally different style of wheeling all together, so hard to compare (get the wheels spinning vs. nice slow steady throttle). Maybe hood riser in the rear to vent some heat might do the trick...
 
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Was that 1,2 or 3 wires on the Universal?

It needs to be three wires!
 
mjma said:
4 wires!!! Is that a problem?
Click to expand...

No, only problem is my memory, LOL. I forgot the newer ones added a ground wire. 4 wires is good. I have seen one wire universals at Autozone, cheaper but may vehicle computers do not like them, and will reject them throwing CELs.
 
Ecomike said:
No, only problem is my memory, LOL. I forgot the newer ones added a ground wire. 4 wires is good. I have seen one wire universals at Autozone, cheaper but may vehicle computers do not like them, and will reject them throwing CELs.
Click to expand...

I'm definitely thinking that the computer isn't a big fan of tthe universal O2 sensor. It is a bosch sensor.....just universal connection on it. I think I'm gonna grab one from the dealer and see what happens.
 
mjma said:
I'm definitely thinking that the computer isn't a big fan of tthe universal O2 sensor. It is a bosch sensor.....just universal connection on it. I think I'm gonna grab one from the dealer and see what happens.
Click to expand...

I doubt the Bosch sensor is the problem. You say universal connector, did it get rewired or something? I would get an multi meter (DVM , Ohm , volts) and check the wires for the proper voltages and grounds. It's easy to do.
 
thats the one i used in my jeep, and the damn thing crapped out, so i took it back and put in a mopar replacement one. well, i figured out part of my problem last night, my fiancee is currently driving it, and wehn it gets low on gas, and you pull out of somewhere and turn sharp enough at the same time, it sputters cause the fuel sloshes away from the sump. common sense, but she doesn't know too much about vehicles yet.......LOL.
 
igotanxj said:
why didnt you get the bosch O2 sensor for your jeep instead of a universal?

It looks like you need a bosch PN 13100
Click to expand...


It's a Bosch universal O2 sensor. The sensor is bosch, but it's not plug and play. I got it from rockauto.com, which has good prices on stuff. It was more expensive than the cheapest regular O2 sensor that has the proper connection on it.

The universal just have 4 wires on it and you have to cut your old sensor wire in the middle and splice it together. After the fact, every mechanic that I've talked to has said that the universal ones are not good for newer vehicles....say they're fine for pre OBD stuff, but not for OBD2. I'll get you folks a pic if you still don't get what I'm talking about. I really didn't know what a 'universal' O2 sensor was when I bought it....I just saw the bosch name and was like "hell yeah."


getimage.php

This is a pic. It's got some crazy splicing box that seals up the splices in the connection. I don't think I'd buy a universal again. Oh well, live and learn!
 
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