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Old 02-28-2009, 10:07 PM   #51 (permalink)
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Join Date: Dec 2008
Location: Placerville, CA
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RippinRoo - '05 Subaru Legacy Wagon 2.5 GT
90 day: 21.16 mpg (US)

Helga - '00 Volkswagen Jetta TDI
90 day: 53.91 mpg (US)

Olga - '03 Volkswagen Jetta Wagon
90 day: 46.24 mpg (US)
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Filled up today... This time I got 44.96 mpg.

I'm a bit frustrated with the comparatively poor FE that I've been getting after the conversion to the Fed ECU. Generally, my FE has been worse since the conversion than before, when using the Cali ECU. I averaged ~47 for the 3 tanks prior to the conversion, and now only ~44 for the 2 tanks since. Route, driving style, and temp ranges have not been that much different.

One of the main things I've noticed (as mentioned in the previous post) is that the idle is really high when stopped and when coasting out of gear. Last weekend, I took apart things, re-re-checked my newly built conversion harness, checked vacuum connections, checked the IACV (Idle Air Control Valve), etc, etc. I also plugged in my original Cali ECU with the new harness and the 5-wire LAF sensor, and it idled just fine (though it did throw a CEL (check engine light)). Mainly I think that verified for me that there is no problem with the IACV, vacuum, or intake in general, and that it's probably related to either the ECU or one of the sensors the ECU uses to set the IACV opening.

During this past week, I was actually able to find another Fed ECU locally (I only note this because I am, of course, in Cali, and finding a Fed ECU locally was a bit surprising). I picked it up today, swapped it for the current Fed ECU in the Maus, and ... it seems to work quite a bit better! I dunno, I guess on the one hand I was hoping for improvement, while on the other hand, I am surprised that there was any difference at all. Can an ECU degrade over time?? I looked at the innards of the ECU that was giving me trouble, and they looked just fine... so very strange, overall.

For the OBD1-to-OBD1 extension harness, I found a guy that says he'd be willing to sell them for $50 each if I buy 5 or more... I obviously don't need more than one, but if there are others on this board interested, I'll set up a group buy thread.

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