I just pulled a heavy load about 400 miles and I love the way my truck runs after a good workout!!!

But the next day I was running empty and noticed I had 14lbs of boost. Mileage was fabulous and throttle response was great, but normally I run 0lbs to 6 lbs on the highway.

What gizmo may be sticking? And do I spray it with WD40 and smack it with a hammer?

 

Only way to get more boost is to run more fuel. Check your boost gauge and check your oil for fuel. Your right at the mileage mark for injector issues.

 

It's run normal the last two days now.

The turbo always spins so what keeps my boost down? Why does it go down when I let off the fuel pedal going 80mph? And what makes it jump back when I hit the fuel again? Isn't there a wastegate or something?

 

Burning fuel creates heat and that exhaust heat is used to spin the turbo.

When you lift the throttle less fuel is injected so the turbo lays down. How ever, a diesel is not air regulated like a gas engine has to be, so the continued air flow cools the engine.

If you had a day or so of increased boost after a day of pulling a load, I would think you are just enjoying the cleaner injectors the load gave you!
Don't worry about it.

A stuck wastegate will only lower the boost unless you are refering to boost at full throttle.
Wastegates are used to bypass the turbine to let heat around it, and to not allow overboost which kills head gaskets, etc.

Yes the turbo is always spinning when the engine is running but only compresses air ( boost) under load.

 

I've driven this truck for 6 years and 140,000 miles and never had the boost idle at 7lbs.

Something was different for two days, now it's back to normal.

 

Probably a gauge issue. No way that turbo is making 7psi at idle...

 

You don't have boost at idle!!!
Try another gauge.

 

^ both these guys are correct, it has to be a gauge malfunction

 

Maybe it was the gauge acting goofy.

What controls the boost? The turbo spins at idle, the air it blows goes somewhere.

 

The wastegate controls the boost. The small amount of air the turbo moves at idle just get used up by the engine.

 

Yes it spins at idle but the motor isn't throttled ( like a gas engine) so it just blows through it.
Remember, it is HEAT that make a turbo work and at idle the engine will be at 350 or less.
Once you push the long diesel pedal ( not a GAS pedal) fuel is added and that is heat.
The wastegate only regulates MAX boost.

 

My turbos spin a good 20-30 seconds after shutdown...