The last 2 mornings it been 22 below here. I let the truck warm up for 20 minutes, starts fine. But the turbo doesn't work until it gets over 3000 rpms. Then it will jump up to 25 psi but as soon as I let up on the pedal to go at a cruising speed it drops right back to 0 psi. The truck was fine after work both days. Just wondering if anyone had any ideas.

Thanks

 

Maybe sticking vanes, bad vgt solenoid

 

Even with sticking vanes, you should get some boost. I'd be surprised to find the turbo not working at all.

I'd lean toward a bad MAP sensor myself. What are you using to read boost?

 

Yeah, there's something else happening here.

 

I'm just using the factory gauge. You can tell its not working right, its a completely different truck in the afternoon.

 

At 22 below, I'd bet the MAP sensor is freezing. If you have time some morning, trying warming it up with a blow dryer or something for a while and then starting and driving the truck.

That's just a hunch, though.