2006 f150 4.2l 2WD rug idle rpm don’t go over 3700 even, after start the truck, start shakes. I have changed sparks plugs ( motorcraft), intake gaskets, fuel pump, intake manifold runner control, compression test is good ( 180 psi all six cylinders), engine exhaust pressure ok ( no restricted exhaust), injectors workings good. I don’t know what else to do. Any help I’ll really appreciate. Thanks.

 

Try replacing the wires and coil pack with Motorcraft only.

I'm sure it has codes if it's doing that. Please post the exact codes.

 

Are you SURE the cats aren't plugged?