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Old 06-11-2014, 08:21 PM
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My O2 sensors are bad? Please help.

Evening Jeepers, I got my 06 WK 3.7 V6 for about two weeks now, and I am having a bad MPG, current I get about 12 MPG (that's about 19.5L/100KM) mix city and high way, while I am waiting on traffic light, the fuel consumption in l/100 km format is almost like ticking up......

I've already changed my air filter, clean tb during the weekend, but no improvement at all,

I attached some plots by torque pro app on my nexus 7, I can understand
O2 sensor 1 on both banks are sort of normal but with frequently touch down to 0V (not on the screenshoot)

But I am not sure about O2 sensor 2 on both banks....... I am not sure at all, please have a look at the log plot








Today I also got Misfire on Cylinder 3,4,5,6, and when I run the torque test,
these three fails

MID:$3d TID:$84
EVAP Monitor (0.020")
Min:0.061% Max:100.006%
Current:0.031%

MID:$70 TID:$25

Min:10256 Max:16384
Current:65520

and

MID:$10 TID:$25
O2 Bank 4 Sensor 4
Min:26640 Max:16384
Current 65520

There is a bank 4 sensor?

Any inputs are appreciated, thanks.
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Old 06-11-2014, 09:34 PM
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Re: My O2 sensors are bad? Please help.

While I am certainly no expert on O2 Sensors, I have had a little experience with them after I thought I had some problems right after having custom headers built.
Here's my take on your graphs:
1. Appears normal...should have many crosscounts above/below the midpoint of .45mv.
2. After cat. O2 is fairly normal for cruise mode.
3. Again, after cat. 02 is fairly normal for stop/go driving, with maybe one idle dip.
4. Appears normal.
5. Essentially the same as 3.

There is no Bank 4 sensor.

I did a thread on my experience and research that may help you a little. Here is the link to it: Oxygen Sensors and Their Role in Engine Management--A Primer

Hope this helps you a little.
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Old 06-12-2014, 01:22 PM
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Re: My O2 sensors are bad? Please help.

Thanks jeepgcoman for your reply and the good write up, I am studying it.

meanwhile, the plots I attached doesn't show the O2 sensors before cat touch to 0V quite frequently, is that normal? or they are dying?
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Old 06-13-2014, 08:52 AM
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Re: My O2 sensors are bad? Please help.

They really shouldn't ever hit 0mv. The more crosscounts you get the closer your fuel trim will be to stoichometric (14.7/1). That's why sometimes you'll see shorter legs on your graph....not as much correction needed at that instant. If they're going to zero and/or 9.0mv I think maybe more correction is occurring than normal. How many miles on your ride? If you have over about 75K on it, you may just want to change them all. I had a "lazy" one at just over 60K, so I changed all mine then. Also, if you have a way to monitor fuel trim (both short and long term), post up some graphs of them. That'll give you a good idea of how effective the O2's are.
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Old 06-13-2014, 07:48 PM
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Re: My O2 sensors are bad? Please help.

having the wk for 3 weeks now and bought it with 83K on odometer already, so I guess they are overdue.

The good thing is, parts are cheap and it's not a hard job to DIY, is it
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Old 06-13-2014, 08:41 PM
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Re: My O2 sensors are bad? Please help.

If you suspect they're not quite right, it's certainly cheaper to replace them than to try and have them tested. Don't know how hard they are on a 3.7, but maybe someone that's done it will chime in. The stock Hemi's are a PITA and a lot of guys have invented new cuss words while doing the job. Mine has headers and it's real easy.
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Old 06-15-2014, 07:47 PM
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Re: My O2 sensors are bad? Please help.

I think I found some pics indicate where those sensors are, and there is a youtube video shows how-to for a liberty 3.7, I assume they use the same engine so they suppose to have the same sensor positions?
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Old 06-15-2014, 08:17 PM
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Re: My O2 sensors are bad? Please help.

I believe you're right. You may want to PM Strongjeff, as he has a hopped up 3.7 in a Wk and probably can answer your questions better than I can. Good luck, and let us know how it goes.
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Old 06-20-2014, 10:41 PM
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Re: My O2 sensors are bad? Please help.

Thanks again for the reply.

I am in the process of packing and moving, so I will order some sensors and spark plugs.
Do the job and report back in early July.

BTW, does bad o2 sensor cause misfire? or maybe the crankshaft sensor need to be replaced as well.
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Old 06-21-2014, 08:34 AM
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Re: My O2 sensors are bad? Please help.

Normally, a bad O2 Sensor will not cause a misfire unless it is so bad that it starts fouling spark plugs. You'd for sure notice this if got to that point. Have fun on the move...ugh!!

It's possible the cam/crank sensor(s) could be on the way out, but I think I'd wait before changing all kinds of parts. Since this is a "new to you" vehicle and you're probably not aware of the maintenance history (if there was one), it would probably be wise to just bring everything current, maintenance wise, so you know for sure the status of everything. If things don't improve, then begin the hunt for possible culprits.
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Old 06-21-2014, 10:44 AM
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Re: My O2 sensors are bad? Please help.

Still trying to know more about the O2 sensors myself as well, but a bad O2 sensor can cause misfires yes, especially multiple misfires. If the O2 sensor is fouled, it could sense a too rich mixture (which it in fact not is), and the PCM will downtrim the amount of injected fuel (reduce the fuel injector pulse width). At a certain point you will get misfires due to a too lean mixture.
The O2 sensor externally should be clean as well, since it should get fresh O2 from ambient air as well, which i believe enters in between the wires. Then it can compare the O2 from ambient and in the exhaust gasses.
Since you have torque on your phone, you could check the LTFT (long term fuel trim) figure. It sits normally a bit above the 0, but at least a single digit. If its running lean due to a bad (fouled) O2 sensor, then you will get double digit negative figure. It means that the PCM is reducing too much the fuel injector pulse width and the mixture becomes too lean to burn well.
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Old 06-23-2014, 08:43 PM
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Re: My O2 sensors are bad? Please help.

I will try to read the number and see.

Today just drive about 250 miles with 90% highway, with a/c on I get 22 mpg
but once I enter city road....mpg is decreasing
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