Hi!
I own a 1999 Ford Windstar SEL 3.8L. There are 2 codes: P0171 System too Lean (Bank 1) & P0174 System too Lean (Bank 2). Last year about this time we replaced plugs and wires (with OEM parts). We are getting ready for a long trip so we but a Cen-Tech computer to try to help diagnose the issues. My husband is an ex-auto technician, but he specialized in Toyota and Honda which isn't incredily different, but most definietly not the same. While driving we watched the (I'm guessing voltage) change on all O2 Sensors and they were constantly changing and were insync with each other (Bank 1 Sensor 1 & Bank 2 Sensor 1, and Bank 1 Sensor 2 & Bank 2 Sensor 2) in other words B1S1 & B2S1 were always insync and B1S2 & B2S2; changed at the same right with in a few seconds of each other. I am also able to view MAF reading, but I can't remember what it was off the top of my head. Any help you can give would be greatly appreciated.

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