Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!

jeep liberty 2004 3.7 trouble codes 0172 and 0171 at the same time

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5 years 2 weeks ago #27757 by overdrive138
i have code 0171 and 0172 dtc's rich and lean at the same time
please help thx

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5 years 2 weeks ago - 5 years 2 weeks ago #27760 by Andy.MacFadyen
The conditions when these faults were logged may give you a clue --- particularly RPM and throttle opening also coolant temperature.

Then look at live data particularly short and long term fuel trims and O2 sensor output voltage at idle and about 3,000 rpm.


Also are there any splits or leaks anywhere in the air intake ? ---- anything non-standard about the airfilter

" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)



Last edit: 5 years 2 weeks ago by Andy.MacFadyen.

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5 years 2 weeks ago #27763 by overdrive138
Hey andy , everything in the car is stock . I do notice that this car has a plastic intake manifold. I also noticed that if i rev the engine it starts to stutter around 4k rpm or more almost as if i had a rev limiter.

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5 years 2 weeks ago #27764 by overdrive138
I also had another code 0137 which i have fixed with replacing bank 1 sensor 2 with a new 02.before that was fixed the car ran horrible smoke out the tail pipe etc. Unfortunately i dont currently own a scanner with live date. I Also did some temp reading on the cat and had a 50 to 100deg difference from front to back could that have anything to do with this? Thx

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5 years 2 weeks ago #27790 by guafa
Hi overdrive,

0137(low voltage) shorted to ground?
0171(lean) shorted to ground?
0172(rich) shorted to voltage?

You should check o2 sensor wires and voltage reference from PCM signal line.

I wouldn't discard 0137 as fixed.

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5 years 2 weeks ago #27796 by wacoeagle
a stuck open t stat can cause crazy intermittent rich issues, if the coolant temp sensor thinks its cold. u may have 2 different problems, like exhaust leak before lambda or A/F sensor.

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5 years 2 weeks ago #27817 by overdrive138
i will definitely be checking the t stat thx guys

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5 years 1 week ago #27834 by kostelectronics
Check also for correct fuel pressure.

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5 years 1 week ago #27854 by Andy.MacFadyen
The possibility of a fuel flow issue can also be added to the list but without live data there is no way to reduce the list of possible causes. A 10 Dollar Bluetooth dongle and an Android app will give you very useable live data

" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)



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5 years 1 week ago #27860 by cheryl hartkorn
check for a restricted converter. ive seen it on v type engines with a clogged cat itll have rich/lean codes at the same time
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5 years 1 week ago #27884 by juergen.scholl
Codes for rich & lean mixtures may be caused by evap/purge solenoid issues as well.

freeze frame and live data will b of help.

An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
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5 years 1 week ago #27905 by overdrive138
I just bought a used verus that ill be getting on weds to run live data etc. From my understanding the code is for bank 1 so i will be checking stft and o2 to see if both banks have the issue . i would assume if it was fuel pressure the code would likely be on both banks

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5 years 1 week ago #27906 by overdrive138
i checked converter temps and front to back temps were different . i dont have a exhaust pressure gauge so I dont wanna change it just yet . i would rather check pressure to be sure as I dont feel the temp test is as accurate.

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5 years 1 week ago #27924 by cheryl hartkorn

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5 years 1 week ago #27975 by Andy.MacFadyen
I find temperature tests on converters can be misleading particularly where there is a pipe bend either just before or just after the pipe. Comparing the pre-cat and post-cat O2 is more reliable. The other test than can tell you if the cat is shattered from a misfire is just thump it with the side of your fist. If it rattles it is a dead cat.

" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)



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5 years 5 days ago #28043 by overdrive138
changed the bank 1 upstream o2 sensor and that fixed the issue rich lean code . my verus just got here so now onto some idle diagnosing. car currently has no codes but the idle is still a little rough more so when its cold, but after it warms up it seems to run better . Also I have a noticeable rpm drop stumble right after snap throttle or hold it at 2k for awhile almost like it wants to die.

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5 years 5 days ago #28044 by overdrive138
when u say compare pre and postcat o2 what exactly am i comparing? thx

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5 years 5 days ago #28048 by juergen.scholl

overdrive138 wrote: when u say compare pre and postcat o2 what exactly am i comparing? thx


You compare the voltage readings of the 2 sensors, the one before the catalytic converter and the one behind it....(of the same bank, obiously).

The front one should show an oscillating or fluctuating signal somewhere between 100 mV and 900 mV . This would indicate that the computer has got fuel control and is able to alter the mixture in order to feed the converter with the proper air/fuel mixture to make it work.

The second sensor, the one behind the catalytic converter, should show a much more stable voltage reading if the converter itself is working properly. This voltage may read around 300mV or 700mV, depending on design and system. With your new verus you can compare the sensors' voltages easily in graphic mode.

If the second sensor shows fluctuating voltages similar to the pre cat sensor - in other words the second sensor is mirroring the first one - then the converter is not doing its job, hth.

An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.

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5 years 4 days ago #28058 by Matts Auto
Rough idle could be dirty throttle plate/housing

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5 years 1 day ago #28153 by rpd1125
I had one of these with exact code. Its just running lean on a centralized part of the intake manifold, meaning a vacuum leak. Take a smile generator and put to vacuum port and fill it up ....usually shows up very quickly but what i found was the the Purge control solenoid was stuck wide open allowing full vacuum to the vapor line to the fuel tank..

Easy test is to remove supply vapor line to the Purge control solenoid which is usually mounted right near or intake or driver side fender, easy test is turn the key on, turn on the smoke generator and if any smoke comes out of the solenoid out of the unplugged port to fuel tank there is your problem.

Almost any scanner will allow you the test ability to perform a purge control solenoid test and it allows you to cycle it in 10% increments and should allow you to see the duty cycle while performing this test. The Purge control solenoid should be completely closed at idle and with KOEO. same test can be performed on just about any chrysler or dodge vehicles. Again very easy to find it, your computer may also show Large evap system leak.


Hope that helps
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