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Old 11-06-2012, 09:43 AM   #8 (permalink)
turbovr41991
Master EcoModder
 
Join Date: Nov 2008
Location: Cincinnati
Posts: 323

Civic CX/HX - '97 Honda Civic CX/HX
Team Honda
90 day: 63.77 mpg (US)
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Quote:
Originally Posted by brucepick View Post
I figured that with your fully rebuilt engine it would do lean burn down to 1800 rpm without any MMO. So my new interpretation is that the need for MMO is not because the engine is dirty - yours is CLEAN!! My guess now is that the cars were built for more standard gasoline without the alcohol and other junk included these days. Just maybe the MMO compensates for that change.
I am still thinking it is something else. If it was a gas issue I would expect the VX to have the same problems on the newer fuel. I am half tempted to bite the bullet and get some pure gasoline from a marina to test this though.

Another thought is a clogged / high mileage catalytic converter. Has any HX owner replaced their Catalytic converter with a Dorman or OEM style? I know mine is still the 230k original HX exhaust manifold and catalytic converter.

I also ordered the OEM EGR valve to see if that makes a difference, but I really don't think it will have much of an effect. Will keep everyone posted though.
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