I have a 97 5.4 with a CEL on and 1131 stored. The code reader I'm using is pretty plane and has no deffinition for this code. Every once and a while I get a rough idle for about 30sec then it clears up. I had it idleing for about 10 min last night and it seamed to be putting out a fair amount ofsmoke. I took it for a drive and then let it idle again with the same amount of smoke coming from the tail pipe.Around 5k miles ago Ireplaced the sparkplugs(motorcraft premium) and coil boots. It also doesn't seem to have the power that a 5.4 should. Any help would be great.
-Phil

 

P1131 indicates the PCM is correcting the fuel mixture for a lean condition, bank 1. One common vacuum leak is in the PCV system, the rubber elbows degrade and will suck a hole in the rubber. Especially on the rear of the intake, just below the idle control valve.