Has anyone noticed at idle (parked after driving) where the turbo spools up (fast enough to be noticeable) for about 5-6 seconds then back down?
This could be after 30 seconds of “idle down” without hearing the turbo spinning even at 70 degrees Fahrenheit outside temp.
Not sure if the boost gauge moves but it’s something I’ll watch for next time.
I noticed it this time prior to shutdown because I had the door open and heard it move up in pitch then back down.
Any ideas what the computer is doing under there?



If you feel like reading my rambling…

My example: A few times I have shut down the truck and the turbo spool down is much more defined as the engine shuts off.
I always found that strange considering it was 45 seconds or more of idle time in park so it’s not as if I drive, slam on the brakes, park and shut it off without consideration to the turbo.
Normally I can’t hear the turbo at idle or at shut down.

I understand the turbo is always spinning but it reminds me of the youtube videos where some guy cranks his ice cold truck, revs the daylights out of it and shuts it off while the turbo still has several PSI of boost.
(That nearly drives me crazy BTW.)

No, my feet were not near the pedals yesterday when this occurred.
Think of it similar to when you start your truck in the morning when it’s cold out.
There is a several second delay before you specially hear the turbo spool up and it’s very defined if you start with the door open.
That’s what it does randomly.

 

I have not noticed this but will make an effort to pay closer attention.

When the tech. did my 400 flash he ran the "self test". The PCM runs through all the system check/test and when it exercises the turbo it's amazing. It gets really loud!.

I forget if this is something we can do, somewhere there is a post about holding down a button at startup to run some kind of diagnostic mode or test mode. We should look into that to see if you hear something similar to what you describe.

 

I hear it as well. I just figured it happened whenever compressor engaged for the defrost or A/C but I haven't confirmed this.

 

I can confirm it doesn't have anything to do with the HVAC.
It did it this morning and I had the power off to the HVAC system.
The gauge does move slightly so it may be 1 or 2 PSI of boost when it does this at idle from 0 PSI.

The advanced mode is engineering mode but I think it's just informational.
I don't remember seeing anywhere on the screens that a driver could run his own test.

I remember you talking about the tests at the dealer with your turbo awhile back.
How high did the test spool the turbo?
I want to hear mine now...

 

I really dont know the boost #'s on that self test but I do know that the cycle runs the vanes through their range of motion, I don't think any boost was made if that's possible.

 

True, probably poor choice of words on my part since it's just spinning the turbo but not needing to produce any "power."