I have a 2014 Ford F150 with the 3.5L Ecoboost. I bought the truck with 33,000 miles and a 6" lift on it back in November. In January, I noticed when I started the truck, I could hear one of the turbos spooling up really high then a soft pop. After the pop the turbo would spool down. My truck would sit for days at a time because I traveled for work. This would happen even after it sat over night. When the weather warmed up, it still does it. I took it to the dealership and they told me it is trapped air in turbo. I'm not 100% convinced they are telling me the truth. Now when I accelerate, the turbos sound like they are growling/grinding a little. I'm still under extended warranty. Any advice?

 

I would check to see if there is any free play in the shaft of the turbo by jiggling it around a little bit.

 

And how would you do that? It's an exhaust-driven turbocharger, not a belt-driven supercharger.....................

 

You take the air intake off, reach inside the air inlet of the turbo and wiggle the little fan. If it rattles or has excessive play, the journal is worn and it needs to be replaced/rebuilt.

I learned this a few years ago from a diesel mechanic as a crucial starting point.

I also just quickly looked on the almighty YouTube, and there are hundreds of videos addressing this topic... just type in something like: excess turbo play

Here's an exaggerated example of a rather large turbo on a modified engine: