Engine noises - help appreciated

[2021FiveOOOOO]

Hello! New to the forum. Avid mustang fan and love everything about the car.



I’ve had almost model year of the s550 and every engine has its quirks but this one is giving me issues. I have a 21MY with the 10R80. Vehicle has 4500 miles, never tracked but drive it a little hard on the freeway at times.



Main issues are that it sounds like there’s a vacuum leak or some sort of leak near the throttle body area (if I give it some gas I can sorta hear it) and a weird intermittent ‘thumping’ noise at idle mostly , sort of like if you hit a wiffle ball bat on something while. The hissing noise is obvious in the video attached but the thump is harder to hear since I can’t locate where it’s coming from. My guess is a vacuum leak then maybe it’s related causing the thump. Had a friend take a look and he thought it might be an exhaust issue.

Took it to a local auto shop since my local dealer is backed up and the tech said he couldn’t find anything wrong, but having driven multiple of these vehicles I think otherwise.

I know it might be small but any input would be greatly appreciated, it drives me nuts and might possibly lead to a bigger issue.

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[left4taco]

Maybe spray some soap water around the area where it might be leaking? Don't spray on the electrical harnesses, etc. And don't do it when the engine is hot-hot. Do it when it's still code/warm.

 

[2021FiveOOOOO]

Maybe spray some soap water around the area where it might be leaking? Don't spray on the electrical harnesses, etc. And don't do it when the engine is hot-hot. Do it when it's still code/warm.

Thanks for the input!

I went and bought a mechanics stethoscope (best investment for $10 to diagnose car problems hands down in my opinion) and actually narrowed the thump down to the fuel system. Seems to have either a loose line or the pump/regulator is acting up. I’ll need a further diagnosis using software to look at the pressure, might be too high especially at idle.

As far as the air leak, not too worried about it at the moment, all air/fuel and vacuum pressures check out so it’s just a minor non-vacuum line. Just makes a sucking/hissing sound when I step on the gas.

will update in case anyone has a similar issue and save them some time & money.

 

[Albertcado]

Thanks for the input!

I went and bought a mechanics stethoscope (best investment for $10 to diagnose car problems hands down in my opinion) and actually narrowed the thump down to the fuel system. Seems to have either a loose line or the pump/regulator is acting up. I’ll need a further diagnosis using software to look at the pressure, might be too high especially at idle.

As far as the air leak, not too worried about it at the moment, all air/fuel and vacuum pressures check out so it’s just a minor non-vacuum line. Just makes a sucking/hissing sound when I step on the gas.

will update in case anyone has a similar issue and save them some time & money.

Do you have an update on the hissing noise?
What are the air/fuel and vacuum numbers you used as a baseline as to it being functioning as it should, or what was the test you performed to conclude those checked out?

 

[robertsampfive]

I have similar sound that just started 2021 gt 1200 miles i only here it warm engine at idle park or drive seems to happen every 5 seconds or so sounds louder in car a thump kind of sound

 

[robertsampfive]

checked my throttle body just putting my hand on intake tube i can feel it. will take a look inside this weekend pretty sure it has a defective or weak spring that is not holding throttle plate shut creating the thumping noise at idle.

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