Hello all, new to the forum. I have a 2009 Dodge Ram 1500 4 x4 with 5.7 litre Hemi. Approximately 30,000 miles. Today for the first time I got a buzzing sound when driving around 65 mph. When engine was in "fuel saver" mode (4 cylinders) the buzzing stopped. When I applied the gas and engine went out of MDS mode and back on 8 cylinders, the buzzing started. Everytime I pressed the gas, I got the buzzing sound and as soon as I backed off and the engine went into fuel saver mode the buzzing stopped. Appreciate any thoughts or comments.

 

Where does the buzzing sound like it's coming from? Also any vibrations accompanied by the buzIng?

 

I also recently bought a 2009 hemi CC and I hate the MDS. For me on the highway when the fuel saver light is on and it is in MDS mode, I get what I feel is a vibration felt through the seat and it feels like the engine has a miss. Obviously it is running on 4 cyls so that explains the miss feeling but the vibration is what I do not like.

In the city I now turn off MDS by using the gearshift and having it display a 5 on the dash which makes a big difference but either way the MDS is not my friend. With all that said, I don't hear a buzzing sound in either mode.

 

Check the exhaust and heatshields around it. Chances are that something is loose.

 

I hate to be vague, but the buzzing sounds like it's coming from "under the hood". Back off gas, it stops. Push gas, it starts. (coincides with MDS going on and off). No vibration that I could tell, and truck seems to be running fine. I was caught in interstate traffic so it was difficult to pinpoint noise. Driving from Chicago to Toronto today so I'll have lot's of time to check it out!