I've got a 2000 Ford Taurus with approximately 83,000 miles. I purchased it used about a year ago, and as far as I can tell, it is a safe bet that it has run on gasoline its entire life. It is a flexible fuel vehicle, so when a station popped up right down the street from us, offering E85, we jumped on it. I wasn't sure how it would take to E85 so I started out with a few gallons. It ran great. We got horrible mileage before on gas and the car felt sluggish anyway, so this change in fuel in a way added new life to the vehicle. I filled her up and went through a tank, then filled her up again. Just this morning, though, the check engine light came on and after taking her in the Auto Zone to pull the trouble codes, it says PO171 and PO174.
PO171 - system too lean (Bank 1)
PO174 - system too lean (Bank 2)
After pulling the codes, I had them erased, so it will be interesting to see if they reemerge. Any ideas on what trouble I might have caused by switching to E85. Should I wait to see if the check engine light comes on again, because perhaps it was a fluke? Could it have been merely a temporary fluke? Will the engine/computer adapt to the new fuel? Should I switch back to regular gas after this 3/4 of a tank is exhausted?
I would prefer to continue using E85 since it burns cleaner. We ran about 170 miles on 10 gallons of the stuff, therefore we got about 17 mpg, which is perceivably not any worse than what we got with gas.