Cranks but does not start
 

Here's the deal. A few months back, I was driving to work and the check engine light started to flash like it was misfiring. About 2 weeks prior I had replaced the coil pack on the 2nd cylinder for misfire. While it was flashing misfire the car was bucking and would not go over about 10 miles and hour I stoped the car and turned it back on. The car started back up, and then started the same thing shortly after. I then turned the car off and tried it again, and this time it would only crank. Had it towed to the Ford dealer, where they told me the engine was bad, because they couldnt get it to rotate fast enough for a compression test. Had the motor rebuilt, and now still having the same issues with cranking but not starting. Had it taken to a new dealership and they replaced a relay, and the starter. Still cranks slow and no start. Had the crank sensor replaced and still no start. Recently threw a code for the flappers foer the intake, and when removed and bench tested the intake checks good. It is getting air and fuel, and says it's getting spark but still a no start. Anybody have any ideas? Would much appreciate it. :-jammin

Do a voltage drop from the positive battery POST to the + post on the starter. And do the same from the starter body to the negative POST of the battery. What are your readings?

Surely you jest!

my thoughts are a clogged catalytic converter. This is just a hunch, but it would give you the issues you are talking about and may not throw a code. One way to test is to remove the cat, and crank the motor, if it runs fine, that's your problem. A couple of questions for you. Has the truck gotten wet on the inside? (bad ECM maybe) Has the truck been sitting for a while? (clogged cat, or bad gas.) When you try to start it is there any smoke coming from the tail pipe? Hope this helps lead you or one of the other form member in the right direction to find the cause. I'm sure you will figure it out, when you do share the knowledge.