Join Date: Jan 2009
Thanked 64 Times in 60 Posts
What year is the truck? Check it for codes too. If you were having turbo or valve train problems, I would suspect it would increase with load and RPM. I'm not saying that those definitely aren't your problem, but I would also look at the fuel system. My guess is you're having some kind of timing issue at lower RPM. These injection pumps often can't reach full advance on timing because the fuel solenoid gets worn out from being subjected to low fuel pressure. Since the VP44 has dynamic timing and changes based on load and RPM I could see this being the problem. At idle with the load of being in gear on it (assuming its an auto), if it isn't reaching full advance it will inject too early and run rough for funny. Then once RPM is increased or load is removed, the timing advances further, and you are now back up to a tolerable range of timing. It probably isn't exactly where it should be but its enough to run alright without the weird noises. That is just a guess though.
If you could fill in your sig with some info about your truck that would really help us help you. Drive train and modification information is really helpful.
2000 2500 reg. cab 4x4 auto 577hp
09 6.7L QC LB stick, 4x4.
TOTAL PERFORMANCE DIESEL 707-545-FUEL (3835)