Hey all.

I've been doing some searching but didn't come up with much. My 211 E55 has had kind of a rough idle problem since I got it. It revs smooth as silk and drives great, but the idle is a bit less than zesty. It's not cam'd V8 lumpy or anything, but it puts a weird vibration through the car which is annoying. Also, when I'm stopped with the car in gear, I get a weird lurching sensation as I'm easing off the brakes. I'm planning on doing a transmission flush soon which I'm anticipating might at least help the lurching thing.

This brings me back to the rough idle. The car has 50K miles on it, just replaced spark plugs and I'm guessing wires are original. I read that normal maintenance on plug wires is 100K miles so I'm "guessing" that this isn't my issue just yet. I still plan to replace them shortly but I want to hit the root of the issue first. I'm also wondering if it might be a motor mount or transmission problem. In my searches, I don't see this issue coming up with the 55K cars as much as the older N/A 55's. I don't see a ton of engine movement with the car idling or revving while parked...and I also don't hear/feel any knocking or banging around which would also lead me to think motor mounts.

Anyone else have this type of weirdness happening? I hope I'm not the only one and I sure don't want to tear into replacing mounts if there is something more commonly known to cause this.

Thanks for the help!!

 

i had all my mounts replaced around 43k. similar rough idle symptoms.

 

What did that cost parts and labor?

 

it would have cost $845.70, but my ext warranty covered the work. work was done at the dealer.

 

E55 I have had. Also trans mount is very commonplace, and I was surprised how much smoother when it was replaced.

 

Allen,

When you say you've had that issue on every E55, does that mean idle shake, or bad motor mounts (and trans mount) that caused idle shake?

Thanks again for all the advice guys!

 

I have the idle problem too....especially when in Park. I just got my Crankshaft position sensor replaced today and my SA said my torque strut bushing is cracking and if i replace that it'll help with the vibrations.

 

The "torque strut" as the Mercedes FSM describes it is a wheel/suspension thing connecting to the wheel carrier. I'd think this would only have an impact on when the car is moving and the chassis is "torquing", not at idle or when the motor is "torquing". Please clarify though if I grossly misunderstood what you said.

 

Your absolutely right KJ... i guess she meet the vibration would stop when i hard brake.. lol so i guess i'm in the same boat as you.

 

more related to the lack of smooth engagement to the supercharger. All my cars didin't have enough miles on them probably give them the idle shake, but I'm sure through timem that they would. I had just found that these items seemed to make more difference in the smooth engagement of the supercharger than the other stuff people talk about here.

 

I just had my left side mount replaced and the trans mount at 54K. i think the total was about 300 parts, 300 labor.

 

What kind of symptoms did you have? I'm also not sure if you knew how they diagnosed that it was bad mounts, but if you do, that'd be stellar to hear.

 

I guess you could say there was some rough idling. I had taken in for a service at the Indy MB dealership and my brother who works there told me the mounts were shot. So, i don't really know what it felt like before b/c they were shot when I got the car. But, again i felt like it was idling a little more than it should have.

 

Thanks for the info. Good stuff.

 

Here's a little update for you guys. I bought some new mounts...motor and trans mount. I figured, what the hell, I'll replace them all. I'm glad I did. I figured I might as well turn this into a little "HOW TO" while I'm at it.


Transmission mount:

The trans mount is pretty easy to find. It hides right under the tail-shaft of the transmission and is held in by 4 bolts...two that hook to the trans, and two that mount it to the transmission cross member. I used a screw jack to "lightly" maintain the weight of the transmission as I removed and installed the new one. DON'T jack up on the pan at all.



Holding the trans level:


I didn't bother looking up the torque specs of the bolts. They weren't in very tight, so I made sure to just snug them up but use Loctite to ensure they don't go anywhere:





Motor Mounts:

I wasn't sure about changing the motor mounts because things seemed pretty solid. I couldn't jerk the motor around much by hand and I didn't see it wiggling much either while the motor was running. When I looked at them, they seemed fine...really nothing to report.

Here's where I went wrong. The motor mounts have this nice white-ish boot on them to probably protect the rubber from dirt and debris. This also hides the true condition of the mounts.

Here's what they look like with the boot covering all the nasties that lie underneath:



Here's what the mounts should look like brand new:



Here's what my driver's side mount looked like. It was pissing fluid all over the place and genuinely hating life. Very much not good any longer:



There is a single bolt on the top and bottom of the mount with tabs on the mount that align things properly. The "proper" way to relieve the weight off the mount is to use an engine hoist which involves having that nifty little mount thing that screws onto the supercharger. I opted to not do things the "proper" way and was able to find a really thick piece of casting on the block on each side to relieve weight with the screw jack. Just move it enough so you can get the old mount out and the new one in.



I haven't had a chance to fire the car up to see if this was the key to solving my vibration issue...but due to the torn mount, I'm sure this can't make it any worse.

Thanks again guys for pointing me in the right direction!

 

good write up thank you

 

any update?

 

Negatory. The car is under the knife at the moment...it'll be a week or so before I can fire it up again. I'll definitely update again once I find out for sure if this was the culprit.

 

THANK YOU!! I just ordered my new mounts too, next week i'll be tackling this

 

Nice writeup! How did you get the mount out from between the engine and frame? Did you disonnect the exhaust, squeeze them past the sway bar, or find another way?

 

I had my exhaust out for other reasons so I'm not really sure what complications keeping it in would pose...but I'd probably recommend pulling it to do this job. It really frees up a lot of room and is only a couple bolts to remove.

 

I was just curious. I pulled mine out without removing the exhaust, but it was tight! Still better than potentially breaking off the manifold studs. I could feel them start to twist when I put some torque on them, and didn't feel like getting the torch out. The top mount bolt is easily removale from the front, but I'm sure taking off the exhaust makes the whole job a lot easier.

 

Here's an update since I was asked if this solved my issue. Yes, the car is a lot smoother now when it's acting normal so I'd concur that this was a successful fix. I've got some other electrical gremlin that causes it to cut the S/C and retard timing and in general shake like an epileptic so that's my next focus of attention.

 

High IATs could be time for a new IC pump.

 

I replaced both motor mounts and the tranny mount. Made a huge difference but there is still some vibration until everything is at operating temperature. It's not drivetrain related, does it in gear as well as in park when I slowly rev it. Never noticed it in the Summer.

I've never driven a new or very low-mileage E55. Anyone else out there have an E that's completely smooth when it's freezing cold outside?