Alright. I just bought this truck at the end of October. Had no (known) problems, until now. 2009 f250 5.4 super duty 4x4 XLT. Just hit 104k. Problem started week before last 1/4/17. When I start the truck it would shake and run rough for half a second, then runs just fine. Going down the road and stopped it runs fine. One time I was backing up, and had to straighten myself out and went from R to D to R back to D then it started doing it again. Put the truck in park, fed it some gas and it started running fine again. That's the only time I've had it happen besides while it's been starting up. I started it up one afternoon, and the check engine light came on. We dropped it off at the local mechanic shop yesterday and just got the news. P0340 P0341 and P0346. The guy says he's not sure what it is, because it only does it while starting (mostly) but most similar problems run rough while driving down the road. He's thinking Cam phasers or valves, but doesn't know for sure. Before I start making expensive repairs, I want to know what the problem is. Any help will be greatly appreciated and thanks in advance!

 

Any ideas? I was on Google all day yesterday trying to figure it out, there's lots of similar problems, but they all include the truck idling/running rough, not just on start up. How do i know if it's Cam phasers or not? Any help/thoughts would be greatly appreciated. I hate to just start throwing money at it until it stops.

 

After reading on this for awhile, I'm going to say the best place to start is at the CMP and wiring. Considering this is intermittent, I am thinking wiring more than the CMP, although the CMP could be going bad. You may have read this article already, but I'll post the link and you should grab your meter and do some testing.

P0346 ? Camshaft position (CMP) sensor A, bank 2 range/performance problem ? OBD2 Trouble Codes

 

Alright, so I finally found some time to look at it for myself. When I went to unplug the sensor, I realized that it came off very easily, and I didn't have to push the pin in to release it. Could this be my problem?

 

In fact, there is no pin, it's broken off..

 

K, so I got the new connector and replaced it. Spliced the wires, easy enough. Now, the truck is in limp mode! What happened!? I'm getting so frustrated with this.

 

Pull your codes but it sound like the cmp is bad to me.
I wouldn't just throw money at it, check your codes. The engine light doesnt have to be on to have codes.

 

Try turning on the key but don't start it and clear codes with a scanner.

 

So with the codes that you listed these are generic power-train diagnostic trouble codes. Meaning they should apply to all cars newer than 1996. The code usually doesn't pinpoint the problem, it usually just points in a direction & you have to go from their.
This is a generic powertrain diagnostic trouble code (DTC), which means it covers all makes/models from 1996 and newer

Read more at: https://www.obd-codes.com/p0346
Copyright OBD-Codes.com

I've got an 03 with the 5.4 & just recently had these same symptoms happen to my truck. At first it started rough for a couple weeks, no codes, & it would be fine after warming up & or starting to drive. Then one day it started rougher than usual & then proceeded to throw a code & my light. Was throwing codes for rich & lean on cylinders. I started by replacing my mass air flow sensor & it immediately resolved the rough start & my light.

Also when you spliced the wires, did you solider them with heat shrink? Or at least electrical tape them up really good? Or did you use those plastic quick splice in connectors? I HIGHLY don't recommend those for long term durability