Need help troubleshooting, not sure what the problem is.

[WhiteKnight]

Before I begin let say that I use Forscan and the car is producing no codes.

 

What is happening is that when I start the car first thing in the morning I get a strong rumbling, perhaps metallic in character sound coming from the front end of the car as I sit in the cabin while it is still in park; it sounds like the engine is trying to die but not dying . This sound will eventually go away as the car warms up to operating temperature. Further, if I open the hood I cannot hear the sound in the engine, I only hear it in the cabin. I have noticed that when the engine turns off there is a strong, short hissing noise almost like a balloon deflating ( hear this in the engine compartment, not the cabin). The car drives down the road properly. It is only when the engine starts and stops and it is very noticeable when the car is in park first thing in the morning.

 

My initial thought was maybe the engine was misfiring but there are no codes for a misfire. My next thought was that maybe it is the engine mounts but I am not getting any vibration in the cabin, just noise. When I open the hood with the engine on the engine doesn't seem to vibrate excessively, there is some vibration but its not actually shaking. It could be the transmission but there doesn't seem to be any issues driving the car. The hiss noise made me think maybe some kind of leak, like a vacuum leak but again I am getting no codes.

 

It's bothering me. Something clearly is wrong but I don't know what it is. I am now wondering if maybe it is dirty fuel injectors but I feel like at this point I am grasping at straws. Any one experienced something like this?

 

2015 Cmax hybrid, 130K miles.

 

Thanks.

 

 

Edited February 1, 2022 by WhiteKnight
added hybrid