Hey guys bought a Canadian 2003 f150 about a month ago. Its got a 4.6, auto trans, 4x4 and 75k miles. Decided yesterday to change plugs for the hell of it. Wasn’t running bad but I assumed it wouldn’t hurt. The old plugs were motorcraft agsf32pm and were worn to the point that the gap was about 0.080. I picked up some autolite ap104’s, gapped them at 0.053. (the sticker under hood said 0.052-0.056) Now it’s smoother but seems down on power. What would cause this? Is the computer trying to adjust to the plugs? Or did the Canadian trucks have something different requiring a larger gap?

 

Try disconnecting the battery for about 10 minutes to kill the 'keep alive memory'. It will start the adaptive learning from scratch.