obd2 code 1131

[MIke713]

Jumped in my 96 ranger 2.3 automatic two wheel drive to head to work and the check engine light came on.Now What? Truck was running fine .I put my scanner on it this morning and it came back O1131 code. what I have been able to find is it is a lean condition . Where do I start the repairs on this . BTW the truck has 66,000 miles on it and I have changed plugs and wires , filters (fuel and air) cleaned the mass air sensor . any help would be great.
Mike

 

[killj0y]

Maybe fuel pump is going out? I've had situations where the pump comes on and you can hear it, but it doesn't build up enough pressure. It's a thought anyways, plugs and writes wouldn't necessarily cause a lean condition. Usually that means not enough fuel is reaching the ignition chamber. I suppose a faulty oxygen sensor could cause this as well.