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Old 01-27-2020, 10:31 PM   #81 (permalink)
Cyborg ECU
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Join Date: Mar 2011
Location: Coastal Southern California
Posts: 5,610

Black and Green - '98 Honda Civic DX Coupe
Team Honda
90 day: 59.47 mpg (US)

Black and Red - '00 Nashbar Custom built eBike
90 day: 3671.43 mpg (US)
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Originally Posted by jimmylomax View Post
... do you think the times the code came back may have been longer stints without EOC? I ask because sometime this summer, I got a P0420 in the Fit on a long commute where I left the AC running for a passenger. I cleared it and it has since come back a couple times when I went longer than about 15m between EOCs.
I don't think it was the EOC as much as perhaps burning a little oil through the valve guides and/or oil control rings. In EOC maybe the leakage does not have as severe an affect on the CAT's efficiency as when the engine goes constantly for 30 mins and more. My second recurrance was under high load climbing a mountain pass into the high desert, so... pretty hot and probably oil burning?

Originally Posted by jimmylomax View Post
Did you run an OBDII scanner and look at the O2 sensor data or measure pre and post cat temperatures? (I've got 30 days to make mine happy to pass my local DOT inspection).
My 1998 Honda has no CAT temp sensors. Wish it did. Some things remain a mystery to me...

You are going to "boil your CAT in acid?"


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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