A little problem.

[B2Mann]

The other day I was driving my ranger, 91, 4.0 5speed, was passing another driver, and noticed, brown smoke coming out of the exhaust pipe between shifts. Anyone have a thought as to what might be causing this? Truck is still 100% driveable besides that.

 

[B2Mann]

Ran codes on it today. Codes im getting while engine is off and running are 41 and 66. 41 being Lean fuel system, and no 02 detected. 66 being MAF curcuit below minimum voltage. I replaced the 02 sensor maybe 6 months ago. Gas mileage is 20-22mpg. Ive never replaced the MAF, but I have cleaned it. Can anyone chime in with some advise?