vibration at idle - motor mounts?

[ftillier]

My wife noted today that the LR4 seems to have some vibration in the seat and steering wheel when at idle. I've noticed it too but didn't mention it to her, so it makes both of us noticing the same thing. Search is rather light on details for how to DIY this, a mention of dropping the front diff along with one video on YouTube showing the access when you do so. The shop manual instructions are rather involved, and I'm not sure how easily removing the catalytic converters will be after 13 years of heat cycling.

So first things first, what are diagnostic steps to confirm/deny that it's motor mounts?

Second, has anyone done the job using the front diff method, and if so what are the steps? Anything to be careful about regarding the diff vent/etc? Are the bolts all reusable? Do you need to remove the axles?

Thanks,
-Fab

 

[Longtrail]

Is the frequency of the vibration similar to that of the motor, what happens when you slowly pick up the revs? These engines are pretty smooth (not the same as a straight six which mathematically is the smoothest) but they're still pretty smooth. Is there another way to identify motor mounts perhaps; so rather than looking at the seat vibration, look to validate if the mounts are considered OK?

Have you peaked underneath to see if anything else is going on?

Sorry, I'm shooting in the dark a little here but wanted too chime in. Really thinking out loud would be to see if there's an accelerometer app on your phone and see if you can measure the vibrations (perhaps compare to others and look at the frequency).

 

[itsaguything]

+1 on @Longtrail ‘s suggestion.

Looking forward to an answer from a pro, too. (@Rover Range , where are you?) The only way I know how to check a bushing or mount is to check for movement/play. And I do that with a pry bar.

Would a scope/camera work while at idle?

But I think you are have the correct initial hypothesis; vibration in the steering and seat concurrently is disconcerting.

About those questions of yours, though its pretty early yet, many would never reuse bolts when it comes to mounts or bushings. (a theme written in most workshop manuals) Its “play” that is an enemy.
Also, did you see the procedure in the workshop manual? It is very detailed.

 

[Rover Range]

Take a look at your air intake tube at the throttle body. If the tube is sitting on the fan shroud, the mounts are collapsed.
Another check you can do is.
In a safe area. Open the hood. Engine running- put the vehicle in drive- foot on the brake- give it some gas- you will see the motor jump up. Do the same in reverse.

 

[ftillier]

Intake tube is above the shroud:

I'll check for engine movement when I have a helper. Haven't had a chance to get underneath, but the 125k oil change is coming up and I do tire rotation at the same time so it'll be up on jack stands.

 

[Rover Range]

You should have about a 1/2" clearance.

When you power brake it, you can see the engine cover from the driver's seat.

 

[f1racer328]

I've noticed the same in my LR4. Same mileage too, about 131k. Haven't bothered to do anything about it since its subtle, but my first thought went to motor mounts too. I'll take a look at my intake tube clearance at some point.

 

[ftillier]

Alright, so I popped the hood open and did the power brake test in D and R, and while I can see a tiny bit of rotation in the motor from the torque, I don't see much movement at all. I guess the good news is that it's not likely to be my motor mounts, but the less good news is I don't know (yet) where it's coming from.

It also only seems to happen at the low idle - fast idle or revving the engine results in no noticeable vibration.

 

[jlglr4]

What are you idling at? Does it surge at all? Does toggling the ac on/off make any difference? Might check throttle body for dirt/gum - could try cleaning it with some carb cleaner, and see if it makes a difference. Clean air filters? If you have a GAP tool or the like, could check your fuel trims to see how they look (people are probably sick of me telling everyone to check fuel trims, but it gives you good info about your fuel mixture).

 

[ftillier]

It idles about 600 RPM, no surging. I'll try turning the AC off and see if it makes a difference. I do plan on removing and cleaning the throttle body this coming oil change as I keep getting a MAP sensor out of range CEL thrown, despite replacing the sensor. I'll also check fuel trims, good idea.