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Old 01-31-2010, 12:06 AM   #6 (permalink)
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Join Date: Jul 2009
Location: New York
Posts: 513

no nickname , it's just a car - '04 volkswagen golf tdi
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decel fuel cutoff

I also noticed that when I coast, it registers as open loop when the injectors cut off. Hmmm... "...

when the injectors are "cut off"
you are probably not coasting in neutral -

when MR ECM sees throttle closed and engine rpm above around 1200 rpm , MR ECM shuts off the fuel
that condition is known as
"Decel Fuel Cutoff"

it will / should not happen at idle when coasting in neutral

"Decel Fuel Cutoff" should happen when traveling down hill in gear with the throttle closed , engine rpm over around 1200 rpm

since the feed back system for controlling mixture is disabled during
"Decel Fuel Cutoff"
the system should be in open loop
other wise
MR ECM would see 02 sensor pinned lean and MR ECM would do everything it could to make the mixture rich enough to get the 02 sensor to start cycling
since fuel would be disabled due to "Decel Fuel Cutoff"

there would be an unresolvable conflict .
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