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Catalytic converter/o2 sensors
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Gasbaa
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Dec 7, 2016, 3:49 PM
Post #1 of 16
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Catalytic converter/o2 sensors
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I have a 2006 Ford Freestar with some bad stalling problems. Threw a p0420 code (catalyst efficiency below threshold). I ran live data and all sensors fluctuates between .1v and .9v. Except for sensor 1 bank 2 which was stuck at .095v. I expect the cats are bad and causing the stalling as there is so much fluctuation on the downstream sensors(so says the interwebs) but I am not knowledgeable about these sensors(plenty of internet research but no experience) and how the o2s12 may be affecting the car. I am guessing maybe replace the o2s12 sensor and see how it reacts? Or should I even bother. Thanks for any advice.
Edit: I think I am somewhat worried that the o2 sensor may be causing the stall. I am more worried about the stall then anything. I'm guessing it's stalling cuz the cat is plugged and pushing exhaust back in the cylinder but again I'm fairly clueless about the o2 sensors.
(This post was edited by Gasbaa on Dec 7, 2016, 4:29 PM)
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Discretesignals
Ultimate Carjunky
/ Moderator
Dec 7, 2016, 5:02 PM
Post #2 of 16
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Re: Catalytic converter/o2 sensors
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Which engine? When does it stall? Does it start back up after it stalls? Have you noticed loss of power when you give it the beans?
Rear O2 sensors usually don't cause stalling problems. You definitely need to figure out the stalling issue before condemning the cats for the P0420 code.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Dec 7, 2016, 5:06 PM)
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Gasbaa
Novice
Dec 7, 2016, 5:11 PM
Post #3 of 16
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Re: Catalytic converter/o2 sensors
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3.9 .Idles fine. Stalls during acceleration. Sensor 1 bank 2 is the one stuck on.095v which would be the upstream sensor? Would that make it stall? Does start back up. Sometimes it dies out completely and will need to be started again but turns over.
(This post was edited by Gasbaa on Dec 7, 2016, 5:15 PM)
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Hammer Time
Ultimate Carjunky
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Dec 7, 2016, 5:59 PM
Post #4 of 16
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Re: Catalytic converter/o2 sensors
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Why would you jump to the conclusion that the sensor itself is the cause is the cause of the high reporting voltage? That's rarely the fault of the sensor it self. What is is telling you is that the fuel is too rich on that bank. A plugged converter is one of the things that can cause a reading like that. Anything else causing a rich mixture could also do that.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Dec 7, 2016, 5:59 PM)
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kev2
Veteran
Dec 7, 2016, 6:20 PM
Post #5 of 16
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Re: Catalytic converter/o2 sensors
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Bank 2 sensor 1 the one reading .095 or is that reading .95? A .095 would have me suspecting the sensor itself.
You can use an exhaust backpressure gauge, or observe engine vacuum holding rpm steady @ 1500 does vac reaingg drop?
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Gasbaa
Novice
Dec 7, 2016, 6:30 PM
Post #6 of 16
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Re: Catalytic converter/o2 sensors
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.095 I took a picture of the readings so I could refer back to that one cuz it was so obviously the odd man out. Definitely .095
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Hammer Time
Ultimate Carjunky
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Dec 7, 2016, 7:04 PM
Post #7 of 16
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Re: Catalytic converter/o2 sensors
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I stand corrected then. That is a lean indication.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Gasbaa
Novice
Dec 7, 2016, 8:28 PM
Post #8 of 16
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Re: Catalytic converter/o2 sensors
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Originally I checked for vacuum leaks using the spray and pray method with some carb cleaner. Figured I would find one but no change in idle. Borrowed a scanner popped the p0420. Ran the live data after searching for solutions on the web and came up with voltages previously stated. Most of my car experience is on volkswagens, old fords and wrenching on old Sh!t bust from what I can scavenge off the web my cats are bad but I'm trying to get some input before I pony up for cats. I looked around for lean on bank 2 sensor 1 and it sounds like most likely candidates are vacuum leak or o2 sensor. Previous owner said he did smoke test a year ago and I got nothing on spraying the cleaner. Any opinion one just spending the money on the o2 sensor or is there a better option. Long winded but I appreciate any advice.
(This post was edited by Gasbaa on Dec 7, 2016, 8:29 PM)
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Hammer Time
Ultimate Carjunky
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Dec 7, 2016, 8:40 PM
Post #9 of 16
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Re: Catalytic converter/o2 sensors
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A vacuum leak is not real likely since you are only getting the lean reading on one bank of the engine.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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kev2
Veteran
Dec 8, 2016, 7:54 AM
Post #10 of 16
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Re: Catalytic converter/o2 sensors
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See if you can force system rich - carb cleaner into TB partially block TB.... see if that .095 changes. A suspicious reading .095 I suspect bad sensor - contaminated with ?
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Discretesignals
Ultimate Carjunky
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Dec 8, 2016, 8:19 AM
Post #11 of 16
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Re: Catalytic converter/o2 sensors
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0.95 volts would be a rich condition if the sensor was working correctly. The fronts switching and the one rear stuck high would definitely be a sensor issue. If you want to attempt to force it low you would have to create a vacuum leak.
Still don't think that the O2 is causing your stalling.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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kev2
Veteran
Dec 8, 2016, 8:36 AM
Post #12 of 16
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NOTE the reading is .095 confirmed by poster - confusing as I initially jumped to rich .95...
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Gasbaa
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Dec 8, 2016, 10:15 AM
Post #13 of 16
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Re: Catalytic converter/o2 sensors
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I apologize but I may have confused the issue. That .095reading is from O2S12. I keep reading it as O2Sensor1Bank2 but I think it should probably be O2Sensor Bank 1 sensor 2. I also found out that the downstream bank 1 sensor(which if I'm right about being confused is the O2S12) was recently replaced and was told the stalling got worse and and has been getting worse since. I appreciate yours guys time and effort. I may just take it into a shop to diagnose but I feel like they are just gonna read the code and tell me my cats are bad.
(This post was edited by Gasbaa on Dec 8, 2016, 10:21 AM)
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Discretesignals
Ultimate Carjunky
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Dec 8, 2016, 11:02 AM
Post #14 of 16
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Re: Catalytic converter/o2 sensors
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Sorry Kevin. That was my mistake. .095 volts.
Wonder what the long and short term fuel trims are?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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kev2
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Dec 8, 2016, 1:27 PM
Post #16 of 16
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