Benzo 003

I just brought my 350 4matic in for what may be emergency service. I drove it to work, beautiful....started it 8 hours later and it vibrated like an old diesel! I let it warm a little, thinking it was cold, 40 degrees here yesterday, but noting changed.
Stopped at a light in gear, the idle speed was exactly 600 RPM. If I brought it up to 650-675, no more vibration. It would reappear at approx 30 MPH/1400 RPM until 45 MPH.
In park at idle, the steering wheel, front seats, floorboards, and pedals buzzed like a beehive, worse than any old American car I've ever owned.
SA at the dealer says they have an 09 in for a total engine rebuild for a similar complaint....anyone have anything close to or similar...any suggestions?
23,500 miles on very fresh oil.

C22

checked the battery?

Benzo 003

I did not check the battery....I did check under the hood and physically felt the engine block vibrating. I removed the plastic engine decor over the pulleys and could fell an obvious vibration coming from the motor itself....no word from the service dept yet....

sosh

With your infinate wisdom tell me how a battery can cause vibration??

am_beagle

Ha, Ha......it's Sosh again.
I am sarcastic too, but you are my favorite model.

Benzo 003

Got the car back on friday.....still not right. The dealer replaced both motor mounts and the trans mount.
After some underhood investigating of my own, I have a request of any and all 350 owners.
I am asking if 350 owners can look at the belt tensioner/idler pully on their vehicle and advise if it bounces/moves in and out, or rolls smooth at idle speed with the engine up to operating temp.
Mine is "bouncy" at idle, then smooths out with more RPMs.
It is located on the driver's side middle of the engine. My pully has a turbo fan look, like cooling fins on it. You will need to remove the front half of the engine cover to get a good look.
Thanks in advance....

Vernl

These motors all have many internal counterbalancers. It sounds like one or more is not doing its job. I have heard of this on rare cases and it requires a teardown of the engine.Also if the damage internally is unacceptable upon teardown the motor will need replacement if indeed this is the cause.Keep us posted

Benzo 003

I did inquire with the SA if it could be an internal balancer and was assured that a "check engine" light would have indicated a more serious problem such as a balancer. I was informed that a replacement "long block" was in the area of 18K....not something the dealer/manufacterer wants to quickly jump into even though an 07 350 was a week into a full rebuilt for a mysterious vibration....hmmmm

Benzo 003

Problem Solved.....on my own I might ad. The dealer replaced both engine mounts and the trans mount....it got a little better. They dismissed the " bouncy " idler/tension pulley as " normal ". So, with the airbox off, the engine ran so smooth that it felt as if it were not even running. I found one of the 4 posts that the airbox mounts to to be loose. I tightened it up and then, I think the key here, took a pair of pliers and pinched the 4 spring load type clips that hold the airbox on the engine almost closed. Remounted the airbox and WOW....smooth as silk.

dgiturbo

I have found that the best fixes will come from the owner. Great job!

Now I haven't looked at the gas motors, but I would think that the unmetered air entering at the clamps should have triggered a check engine light?

gsrjc

good job in finding the problem and also helping the rest of us out.

Benzo 003

Thanks and....the gas engine airbox box channels all of the air toward the firewall and directly into the mass airflow sensor after being filtered. I only ran the engine for several minutes without the box on - no errors.