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Old 02-20-2015, 10:36 PM   #8 (permalink)
California98Civic
Cyborg ECU
 
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Join Date: Mar 2011
Location: Coastal Southern California
Posts: 6,299

Black and Green - '98 Honda Civic DX Coupe
Team Honda
90 day: 66.42 mpg (US)

Black and Red - '00 Nashbar Custom built eBike
90 day: 3671.43 mpg (US)
Thanks: 2,373
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Quote:
Originally Posted by Old Mechanic View Post
Check to see if the fuel rail will hold pressure....
Thanks, as ever. I went out and rented the pressure tester based on this advice but probably can't do anything tonight with it. But I checked the FSM and the regulator is closest to the number 4 cylinder, which means it is as far from the 1 and 3 as it could get.

Quote:
Originally Posted by darcane View Post
...So, a negative fuel trim means that the O2 sensor is reading rich, so the computer is cutting fuel to compensate for it.
So then in the scenario OldMech describes above, the computer is radically cutting back how long the injectors open because the O2 is detecting too much fuel due to pressure regulator diaphram leaking into the intake manifold. There is clearly unburnt fuel in the #1 and #3 cylinder (I can smell it when I pull the plugs out).

Thanks! I'll run tests tomorrow and report back.
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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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