Greetings all. I have hit a wall and need some direction.

On my way home from work on Friday, my 05 5.4 started a shudder. As I was driving I pulled the pending code and all that came up was P0171. I made it home and traced the vacuum lines and I found the offending EVAP hose that was crumbling. I put on a new hose and fired up my truck. It felt good until I put it in gear. At that point, it started to shudder again, here and there, but still a shudder. When I test drove it for a few minutes, I started getting a few backfires and no power, then the power came back and I drove it home. The code I pulled was a P0357. I pulled the COP and put on an old OEM (Early last year, I put in new Motorcraft plugs and aftermarket COPs. I had a bad plug and a bad COP, put in replacements and all was find). No change. I put on another old OEM COP with the same effect.
My battery decided it no longer wanted to work in negative temperatures and died. I put in a new battery. I tested the ground and the pulse wires going to the COP from the PCM and also validated the results by trying another COP wires. Since it all looked good, I bought a new plug and put that in #7. No change.
What might I be missing? What have I forgotten? Any direction is greatly appreciated!

 

Update...
I tested the ohms from the PCM to the #7 connector - .5 to .3 - so that is good. I tried testing the cranking negative power from the PCM with my multimeter, but I don't trust the readings as I am not sure I was doing it right (settings on the multimeter). I tried cylinder #1 and had similar readings.
In order to rule out plug and COP, I put the original plug and COP from 7 into port 1 and put the plug and COP from 1 into 7. I just test drove the truck. It has a rough idle but when in neutral or park and I rev the engine (even held it at 2k) there was not a miss or shudder. When I put it in gear, it shuddered and when it idled, the same. It ran smooth until I hit about 40, then it lost power and started to shudder again. No backfires this time. When the I hit about 30, it seemed to be fine, move over 30 and it was rough again.

I am really confused by this and don't want to have to have a dealer or mechanic diag it... but I might need to tomorrow if I can't get this figured out. Any help would be appreciated.

 

Swap fuel injectors see if the code follows.. and check the condition of your Fuel Pump Driver Module.

 

This engine very fussy about ignition condition .It will show up under load . You must change all boots they keep 30,000 volts from jumping to head ,plugs can be a problem the sp515s are known to fail right out of the box, New ones are sp546.
Boots need a small amount dielectric grease on each end . It is an insulator not a conductor keep it mostly off metal parts. Keep hands clean esp if you use anti seize ,that stuff will short out your spark.
Not fond of aftermarket cops , clean all contacts of cop s real well any low volt plug without a good lock-- change out.
Yes Tech rep is right ,check and upgrade your FPDM on rear axle if its not bad it probably will be . Fuel filter should be changed.
We like to clean out carbon that surrounds the plug snout with carb cleaner as it breaks plugs on the way out and can break them on installation also .
I use a very small amount of never seize on plug threads .All plugs torque in 25 to 28 foot pounds not by feel .
You may need a homemade smoke machine to test for more vacuum leaks , the alcohol in fuel is hard on system . The purge valve itself sometimes leaks.Vacuum system goes many places . .
We will see how you go from here

 

Thank you for the reply TechRep. I had already dropped it off at the mechanic. After about a day of troubleshooting, he could not find the issue either. He said that he was able to get it up to 70 by babying the truck and I should be able to drive it today and to bring it over when I was done to see if there were any new codes.
This morning, about 3 minutes into my drive at 60 MPH, it started missing again and lost power. I made it back home and when the shop opened, I drove to the shop. On the drive over, I finally received a CEL I read the code and it was P0303. I told the mechanic and walked home to wait.
He called me mid-day and told me that he had cleared the CEL and tried to get it to duplicate the code - only P0357 and P0171 came up. He could not find anything and he referred me to another shop that had a better computer.
I drove it home and decided to change all the COPs and the plug in #3. Started it up and it ran perfectly. I am guessing that my battery going bad must have done something to a few COPs? Maybe the plug too? The mechanic had done an Ohm test on the COPs and they call were at the right Ohm reading. I have a working truck, so I am not going to worry about the COPs I removed or the plug. Just happy it is running.
Oh, side note, the mechanic did find an issue for theP0171... The hose that I purchased at Advanced for the EVAC that had a hole was collapsing when the truck was at running temp. He put on the correct hose and that took care of the P0171 error.

Thank you for your suggestion!

 

Redfishtd, Thank you for your post as well. I changed the COPs to aftermarket (high rated) and plugs in March. I had one bad plug and one bad COP out of the box. Otherwise, it was all running perfectly. My FPDM failed a few years back and the new one, with the spacer, has been holding its own. I hate putting the plugs in at 25 foot pounds. It seems like too much pressure, so I hold my breath and hope for the best.