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Old 05-03-2015, 04:51 PM   #3 (permalink)
Cyborg ECU
California98Civic's Avatar
Join Date: Mar 2011
Location: Coastal Southern California
Posts: 6,297

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)
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more reading, more thinking outloud

Maybe I can rule out the vacuum leak idea, because if the ECU is reducing fuel the must either be more fuel getting into system than ECU expects or less air. A vacuum leak would mean more air getting into the system, which the ECU would adjust to by adding fuel, not subtracting it.

Maybe I can also eliminate the O2, since the problem occured during open loop in cold start this morning. In closed loop the idle stabilized as the system detected a rich condition and took away fuel. Maybe eliminate the MAP sensor too, for the same open/closed loop reason.

This leaves fuel injection or a fuel leak from somewhere.
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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