6.4 powerstroke. Runs bad below 42 degrees. Help Please!
 

MY dad has an 08 6.4L powerstroke. When the outside air temprature hits at or below 42 degrees farenheit, the truck acts as though it is in its warm up mode. Boost will not go above 25 pounds and engine makes alot of diesel clatter. As soon as the outiside air temprature goes above 42 degrees the engine runs great. We have had it to several dealers and they all say nothing is wrong with it. But there definately is. There is no check engine light or codes stored in the system. Can anybody please help us??

does it act like this after it has warmed up or is it just on start ups and the first 15 min of driving it?

The whole time. Even after eight hours of driving it will still do it as long as the outside air temprature is below 42 degrees.

the only thing i can think of is the truck thinks its warming up. the 6.4 we had only did it on warm up.

Right. But What Im trying to figure out is why I constantly thinks that. All the IAT and coolant sensors read normal. This started after a reprgram of th PCM by the dealership. Since then its been reprogramed several times for update purposes.

i have run into this before with guys that don't have a winterfront on the truck. put a winterfront on and it will be back to normal

i think the pcm updates have something to do with it. have them reflash the update that they installed whenever this started happening and see if it was incorrectly updated.

this won't change anything. its not a programming issue. i thought the same thing but was assured by the big dogs in engineering that it isnt. the winterfront is the only fix

Is he running biodiesel? I know nothing about Diesels but Biofuel can gel up if it gets too cold depending on the feedstock used. A fuel line heater would help in that situation.

u should see what an IAT sensor is worth and change it, just to rule that out. i think theres two of them. and maybe an exhaust back pressure sensor, the clanging is just the computer changing the timing because a sensor of some sort is telling it to.....not sure what the iat sensor is worth but i think i paid a little over $150 CDN for the EBP sensor when it went.

EDIT
When my ebp sensor went on me, it was usually the colder days it acted worse and it caused all kinds of funky issues with the engine, but no engine light. i had a winterfront on it and it still made all kinds of clatter/clanging, boost would go all the way to 53psi and ive never seen it that high driving it hard even on the SCT tunes, and it still had no power, started making the tranny shift funny....these trucks really seem to have a mind of their own.

....never noticed the date of the last post