bozapp

On my s 430 if the driver door is open you can see it bouncing with engine rotation.there is no check engine lite on and tends to smooth out off idle still has good power no hesistations and it has 83.000mi. does anyone know what this can be?

tusabes

if there is no misfire, the transmission or engine mounts are worn out

ChapelHillMBFan

Yep. My rough idle was cured with new motor and transmission mounts.

bozapp

Ill check the mounts to see if there leaking or do they have to be broken or just collasped to cause a shake @ idle. Or could it be plugs and wires?

marktan

The trans mount is like $25 on Amazon/ebay...not too hard to replace.
About the size of a large softball. My mechanic charged me 0.5 hour (minimum) to replace it, but it really only took him 15 minutes once he lifted the car up.

If you haven't replaced the plugs I'd look there first. FYI, 2 per cylinder.
Also check that the ignition wire boot is snug on the wire. My wife's E500 had a slightly rough idle, also no codes, and it turned out that two of the plug wires (different cylinders) were loose. Cleaned them off, plugged them back on tightly, and no more vibration.

bozapp

Very informative thanks for your input I will check the ignition wires for looseness and while I'm at it ill check the condition of the plugs I may as well replace them so I will have that peace of mind since I have not had the car very long. Then Ill go from there.

tusabes

it makes much more sense to check/change the tranny mount first.
The tranny mount is $25 and 15 minutes labor

there are 16 plugs so about $100 and several hours labor. Plus numerous people have screwed up their car when trying to DIY the plugs and wires as preventive maintenance, when there wasnt any problem

bozapp

Finally did plugs and wires runs smoother but still has less of a shake @ idle. Not as bad as before. Dealer told me I have one bad engine mount. I will try both mounts and see if that takes care of the rest of it.