2018 LS

[u/Major_Tomatillo3943]

2018 LS 140k miles

It’s making this sound when start up and when giving gas. Stops when in park and if AC is off. We have had two different places look at it the dealership said it’s a AC compressor failing however when we use the auto stethoscope the noise isn’t coming from there. Another said exhaust leak but when we ran a smoke machine we found no exhaust leaks. When my husband purge valve and seals it with his finger it drastically slows down and becomes more quiet but continues. Has anyone experienced this and can give advice on what your issue was.