Throttle down - sounds like a blow off valve!

YYZRCYYZRC Member Posts: 5,464 ✭✭✭✭✭
in Engine Discussions
Any idea why my 6.2 has a hiss noise when throttling back (no load)?

https://youtube.com/shorts/U67Zm0T-puo?feature=share
2006 390 EC
2008 350 EC
Georgian Bay
· Share on Facebook

Comments

  • PickleRickPickleRick Member Posts: 4,371 ✭✭✭✭✭
    Usually a hissing noise is associate with a vaccum leak.  


    Hopefully a vaccum hose has popped off.  At idle someoene who vapes can find it pretty easily if they can blow smoke over the top sides of the motor
    · Share on Facebook
  • YYZRCYYZRC Member Posts: 5,464 ✭✭✭✭✭
    edited June 2021
    No vapers here. Would a vacuum leak make the sound you hear in the video - only when throttling down?
    2006 390 EC
    2008 350 EC
    Georgian Bay
    · Share on Facebook
  • PickleRickPickleRick Member Posts: 4,371 ✭✭✭✭✭
    My cell phone has crappy audio so I cant make it out 100% but your description of a hiss is the noise an air leak would make (naturally aspirated engines make the most vaccum at idle) 

    I bet you'll find a little hose that has popped off. 




    · Share on Facebook
  • Aqua_AuraAqua_Aura Member Posts: 2,705 ✭✭✭✭✭
    It does sound like vacuum. It seems like the sound is still there at idle as well. Haven't messed with a carbureted engine in a long time but I believe when the throttle is closed it creates more vacuum and that's why you hear it louder on throttling down. 
    1997 Bayliner 3988
    · Share on Facebook
  • WillhoundWillhound Member Posts: 4,241 ✭✭✭✭✭
    Yep, take the spark arrestor off ( watch that little nut or washer doesn't go down the throttle body) and check for a smaller hose that just pushed on to a nipple near the base of the throttle body/carb. Makes that exact noise.
    "Knot Quite Shore" - 2000 FV270 (Sold)
    2018 Cherokee 39RL Land Yacht (Sorry...)
    · Share on Facebook
  • YYZRCYYZRC Member Posts: 5,464 ✭✭✭✭✭
    I don't see where a hose connects as per the parts diagram?


    2006 390 EC
    2008 350 EC
    Georgian Bay
    · Share on Facebook
  • davidbrooksdavidbrooks Member Posts: 1,432 ✭✭✭✭
    Not sure about the carborated models but on the EFI ones if you have a vacuum hose disconnected you will also notice a difference at idle.  It happened to me once and i thought i had a bad MAP sensor.  Turned out to just be a disconnected hose.  
    It's 5 O'Clock Somewhere!
    · Share on Facebook
  • YYZRCYYZRC Member Posts: 5,464 ✭✭✭✭✭
    Idle is perfect - smooth and identical RPMs to the starboard motor.
    2006 390 EC
    2008 350 EC
    Georgian Bay
    · Share on Facebook
  • davidbrooksdavidbrooks Member Posts: 1,432 ✭✭✭✭
    What about an exhaust leak?
    It's 5 O'Clock Somewhere!
    · Share on Facebook
  • Aqua_AuraAqua_Aura Member Posts: 2,705 ✭✭✭✭✭
    edited June 2021
    Exhaust leak shouldn't sound that smooth. 

    According to some old post on another site there is only 1 vacuum line that goes to the cool fuel module. 
    1997 Bayliner 3988
    · Share on Facebook
  • YYZRCYYZRC Member Posts: 5,464 ✭✭✭✭✭
    I checked the vac line to the cool fuel (there's a tee in that line as well) and it all looked ok.  Will check it again this weekend.
    2006 390 EC
    2008 350 EC
    Georgian Bay
    · Share on Facebook
  • rasburyrasbury Member Posts: 8,962 ✭✭✭✭✭
    Make the hose is not cracked or something...
    · Share on Facebook
  • YYZRCYYZRC Member Posts: 5,464 ✭✭✭✭✭
    edited July 2021
    I think I found the source of the sound. Is it possible that it’s the IAC valve? Maybe the filter is ajar. Will check tomorrow. 


    2006 390 EC
    2008 350 EC
    Georgian Bay
    · Share on Facebook
  • YYZRCYYZRC Member Posts: 5,464 ✭✭✭✭✭
    https://youtu.be/RXoCCMxX3Ug
    2006 390 EC
    2008 350 EC
    Georgian Bay
    · Share on Facebook
  • aero3113aero3113 Member Posts: 9,853 ✭✭✭✭✭
    Big difference 
    2008 330EC
    · Share on Facebook
  • mattiemattie Member Posts: 1,322 ✭✭✭✭
    I was gonna suggest that the IAC might be plugged. 
    246BR, 276BR, H310BR current
    · Share on Facebook
  • Liberty44140Liberty44140 Member Posts: 4,414 ✭✭✭✭✭
    Wow! I’d heard that without it was a noticeable hiss but that is more than noticeable. Nice cheap and easy fix!
    07' Cruisers 390 (Previous Rinker's: 06' 342EC & 01' 310FV)

    · Share on Facebook
Sign In or Register to comment.