Hey, Guys.New Member. I really could use some help here. I've never seen anything quite like this. So my friend has an 07 4.6 Mountaineer with 140k the guy that owned it before him never changed the plugs. After an afternoon of cranking them out,I reassembled and the motor purred like a kitten. I was estatic. So I get in turn it over with a proud grin on my face and shift into reverse. The car starts going bam bam bam violently,like the torque converter is locking up. I manage to back out keeps doing it then CEL goes on,one code only. U0100. Transmission not communicating with the TCM. I read somewhere that it can be caused by a bad coil causing interference with the signal. I spent ten hrs trying to diagnose this. If anyone has any advice,please let me know.