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Old 05-21-2018, 01:07 AM   #169 (permalink)
Cyborg ECU
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Join Date: Mar 2011
Location: Coastal Southern California
Posts: 5,279

Black and Green - '98 Honda Civic DX Coupe
Team Honda
90 day: 59.78 mpg (US)

Black and Red - '00 Nashbar Custom built eBike
90 day: 3671.43 mpg (US)
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Originally Posted by mpg_numbers_guy View Post
How bad would they be? Would it be possible for it to go bad and still get these MPGs by hypermiling, but get even better after replacing/cleaning?

RPMs are consistently dropping out of "warm up mode" at an engine coolant temp of 71C.

Would it be possible for something to throw the error without it existing? I reset it a while back and it returned about 5-10 seconds after starting my car.

EDIT: and is it possible to ruin the O2 sensor by cleaning it?
I think whether cleaning ruins o2 sensors is a matter of how you do it. Do what others have done with success and take it easy and it should be fine. I think if you have an intermittent failure it will come back, sooner or later, sometimes sooner, sometimes later. I do think CELs can get set off in error. It is just voltage fluctuations that communicate the messages to the ECU. I think old machines learn new tricks.

I got my P0420 again tonight, despite cleaning the sensors the other day. My next move is clean the CAT itself, since I now can eliminate the O2 sensor as the source. Science!

See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.

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