Strange miss with a noticable knock
 

Hey guys, my father in law just picked up an 08 XLT 5.4, when coming to a stop it has a bad miss with a noticeable knock. It only lasts about 4-5 seconds and goes away once it is back to idle. No CEL or dummy light come on, we haven't checked for codes yet but will in the morning once it's light out and it seems to happen every 30-40 miles. Any ideas?

We checked for codes yesterday and nothing came up.

Did you run the test at a real shop or have someone like autozone do it? Reason I ask is because the scan tools the parts stores have will usually only pull a code of the light is still on. A dealer or a good mechanics shop will be able to pull a stored code out of the cpu. Like if you have a coil pack misbehaving it may not throw a cel but the cpu knows what's going on.

We pulled it of my hypertech programmer