I am having a problem that I first thought could be transmission until I read this post... My second thought was a misfire.

My miss is right around 45mph, right after the shift into OD. it's very very light and hard to pick out sometimes. Of course no CEL is on, since it seams like half the motor would need to dislodge itself before it would come on. My question is how exactly do you pinpoint a light miss like I'm describing. The plugs are brand new less then 1000 miles. They are motorcrafts. The wires have about 15k miles on them.. They were with my 4.6, the coil packs are original and have 139k on them. It's a slight possibility that when I was doing my swap I mixed up the packs with the ones that came with my 5.4. The guy I bought the motor from was going to put it in a mustang so my 5.4 came with a couple extra coil packs on the mount brackets. So I picked the two brackets that would work the best. Short of changing out the coil packs and wires what is the best way to troubleshoot this?

To avoid any confusion
Motor is a 5.4 out of an 01
Truck is a 98 that had a 4.6 so it has coil packs not COPs

 

What brand are the wires?

 

I think just house brand... If I remember right they were fine on my 4.6...

 

Might want to throw a set of MC's on it - I think they are about 70 bucks at Rock Auto. If you need coil packs, the house brands are usually OK.

 

House brand ? lol. Yea, start there.

 

Man what a bear to change all of those out... Is there no way to narrow it down?

 

Not without a Blinking CEL. You can scan it, you might get lucky (I have). You can push the engine right at the miss point to force a CEL (Done that as well). The CEL doesn't stay on, - you know that right?

 

To be clear - The CEL does not have to be on to set a DTC on the KAM.

 

And, if you you have a scan tool (or equal) that can read mode 6 data, it's pretty easy to identify the culprit cylinder(s).