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Need help on and O2 sensor issue
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dmac0923
Enthusiast
Feb 15, 2009, 1:27 PM
Post #1 of 5
(2740 views)
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Need help on and O2 sensor issue
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2002 nissan Sentra SE-R Spec V
2.5lte 4cyl
6sp man trans
71,000 miles
this car has a pre-catalytic converter right in the exhaust manifold that in notorious for breaking down and getting sucked back into the engine cause catastrophic engine damage.
that being said my manifold...no longer has the kitty.
natuarally there is an O2 sensor before and after the Cat on the manifold
in order to avoid the P420 Check engine light "Catalyst Effeciency Below Threshold" i used two anti-fouler plugs on the lower O2 sensor.
now im getting the P1147 code which i believe is manufacturer specific to Nissan for a bad lower O2 sensor.
the only problem with this is that this will be the 3rd sensor in the past year.
why am i burning through O2 sensors??
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2015 Jeep Grand Cherokee
2002 Ford Ranger
2004 Toyota Corolla
1969 Ford Mustang Mach 1
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Guest
Anonymous Poster
Feb 15, 2009, 8:18 PM
Post #2 of 5
(2733 views)
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Re: Need help on and O2 sensor issue
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With that kind of a setup, it sounds like you are trying to trick the ecm into believing you have a working cat by pulling the rear o2 out of the exhaut stream so it sees a difference in switching times between HO21 & HO22 and not get a P0420, it may work and since that year doesn't use a rear fuel trim stategy it shouldn't affect performance.
The problem is that the ecm does run tests on the rear o2 under certain conditions to make sure it can reach max voltage. With your setup, it can't & you get a P1147.
As for burning thru o2s. This is definately something that wouldn't be trouble shot so I could only take a wild shot in the dark.....
My guess would be that you have your rear o2 so far out of the exhaust stream that you are constantly running the heater & burning up the o2...
You can probably guess what my suggestion for the fix would be 
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dmac0923
Enthusiast
Feb 16, 2009, 4:46 PM
Post #3 of 5
(2720 views)
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Re: Need help on and O2 sensor issue
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wow your right on the money.
thinking about it i bet your right about the heater burning up the sensor. especially since they all seem to last about the same length of time.
so whats your opinion on this idea.
i think what im going to do is plug the factory O2 sensor bung. and install another bung further down stream in the exhaust and using a o2 sensor wiring extension to reach????
if i move the o2 sensor say 8-10" depending on the length of the wiring extension.....would that be enough distance to give the proper catalyst differential and avoid the p420 code?
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2015 Jeep Grand Cherokee
2002 Ford Ranger
2004 Toyota Corolla
1969 Ford Mustang Mach 1
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Guest
Anonymous Poster
Feb 16, 2009, 11:25 PM
Post #4 of 5
(2713 views)
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Re: Need help on and O2 sensor issue
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To be honest I'm suprised that with this setup you aren't getting a 420 (but I do believe you when you say you aren't)
What you are trying to get done is something I actually wouldn't be able to do, so I've never looked in to..... Like I said I'm just guessing... I could be way off.... It could even just be bad O2s.... I've had bad luck with Bosch & try to go OE.
Sounds like you understand the crosscounts & differenial, but the problem is when the ecm checks the rear o2. I'm just going off memory right now but one of the intrusive test it runs is during decel it'll give a shot of fuel to spike the voltage on the rear o2 to see around .78mv or .82mv (don't quote me), if it doesn't then you get you 1147. I don't see how you could bypass that....but then again I would've guessed your current setup would've worked so who knows... that's the best I can do......... I would have to put a cat & o2s on it to fix the prob..
Just remember we are talking about millivolts.... So whatever you come up with just make sure in doesn't envolve current....don't wanna make things worse...
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dmac0923
Enthusiast
Feb 17, 2009, 1:47 PM
Post #5 of 5
(2704 views)
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Re: Need help on and O2 sensor issue
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before i go and plug up one hole and weld in a new bung what ill do is try removing one of the antifouler plugs off the rear 02 sensor.
im pretty hesitant to re install another exhaust manifold that has the catalytic converter in it. if you do a search on the 2002 Spec V 2.5l QR engine they are notorious for eating through and breaking down that Cat and getting the debris sucked back into the engine causing catastrophic engine damage.
well actually if you search for the 2.5 QR youll find several issues that can lead to an engine fatality......
intake runner screws not locktited, getting loose and sucked into the combustion chamber. (fortunately i caught that and locktited them before i lost any.)
headgaskets blow out frequently ( i had this happen and wipe my bearings, fortunately it was under warrenty and Nissan replaced the block for me at no cost!!!)
and the Cat issue. ( i took care of it so that wont be a possibility lol)
stupid me didnt do my homework before buying this car which was the first year for the model at the time DOH!!!!!
__________________________________________________
2015 Jeep Grand Cherokee
2002 Ford Ranger
2004 Toyota Corolla
1969 Ford Mustang Mach 1
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