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!

02 altima 2.5

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4 years 10 months ago #30908 by Tonymac
02 altima 2.5 was created by Tonymac
Hi have issue with 02 altima 2.5 fuel trims are negative on short and long term they are around -21% at idle only when driving they even out around -3/ +3car also has
Code p0420
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4 years 10 months ago #30916 by Chad
Replied by Chad on topic 02 altima 2.5
I'm moving this thread to the "Post your Repair Questions" section.

Does this car have a vacuum controlled fuel pressure regulator? If so, pull the vacuum hose and see if you can see, or smell, any fuel.
"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer."
I have learned more by being wrong, than I have by being right. :-)
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4 years 10 months ago #30917 by Tonymac
Replied by Tonymac on topic 02 altima 2.5
Sorry new to this site still learning where to post .No the car has no pressure regulator
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4 years 10 months ago - 4 years 10 months ago #30918 by Chad
Replied by Chad on topic 02 altima 2.5
A few questions:

How is the drivability? Is there any loss of power?
Any bad smell?

Are your O2 sensors active?
Can you force a lean condition by creating a vacuum leak? (i.e. disconnecting brake booster hose?)

Any MAF, or MAP data pids?
"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer."
I have learned more by being wrong, than I have by being right. :-)
Last edit: 4 years 10 months ago by Chad.
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4 years 10 months ago #30927 by Tonymac
Replied by Tonymac on topic 02 altima 2.5
O2s seem to be fluctuating up and down sometimes both have same reading and maf reads 0.38lb/min at idle
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4 years 10 months ago #31045 by Crombie
Replied by Crombie on topic 02 altima 2.5
Both O2 sensors having the same reading is the cat has failed, if you mean pre and post o2 sensors, are you viewing the sensors on a graph?
Maybe the rich condition is the cause of the failed cat. Thats the worst of it, but I'd do more extensive testing
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4 years 10 months ago #31046 by guafa
Replied by guafa on topic 02 altima 2.5
Hi everyone,

Fluctuation on both O2 sensors (upstream and downstream) is normal when cat is cold. Make sure to warm up cat enough to check it.

Like Chad asked, any driveability issue?

Check if trim numbers change at idle, when you unplug the hose which carries vapours from canister to intake manifold
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