Have been working to resolve rough idle for 1.5 years now.

From time to time, I seemed to have gotten it under some control (w/use of different gas/techron/lubro moly products), but lately it had gotten worse.

Although I do much of my own work, I do have a very good local independent mechanic (who bails me out when I get in over my head) and who offers free inspections once a year. I had been taking my wife's car in every year for this check up (wife cannot tolerate the thoroughness her in-house mechanic applies when performing repairs - considers him too slow), but this year decided to take my '90 300E in. Mechanic noted 3-4 problem areas - including worn motor mounts. I had, of course read about this as potential cause of rough idle on this forum, but had been seeking electrical/fuel related solutions, so had not yet considered this.

Since my idle problem had worsened over time, I asked him to go ahead and replace the mounts, and the transmission mount.

Amazing change! Amazing improvement!

I can barely tell the car is running now!

In case anyone else is at wit's end on this idle issue, you may wish to give another thought to those motor mounts - they really do make an incredible difference!

I am about to do that!

I talked to my mechanic and he said that if I suppied the parts, the total price INCLUDING THE PRICE OF PARTS would total $300...

Is that fair?

I can get both engine mounts for $100, the trans mount for $20... so that makes $180 in labor...

What did you pay?

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2006 BMW M5 "Heidi" @ 109,000 miles
2005 MBZ C55 AMG "Lorelai" @ 165,000 miles
1991 MBZ 300E "Benzachino II" @ 165,000 miles
1990 MBZ 500SL "Shoshanna" @ 118,000 miles

(On the hunt for a good used M103 engine as of 6/10/23, PM me if you have one to sell!)

Please don't pay someone to do this job. It's very easy, and you probably only need the passenger side motor mount which is ultra easy to get to. Just jack the engine up from underneath with a wood block, then swap the mount. Will seriously take you 30 minutes tops. I would be surprised if it took you longer. This is a very very very easy job for any DIYer. Sounds scary, but it really isn't. I bought a pair of motor mounts on eBay for $70 shipped (look for a guy called rojoimparts). Only needed one (the passenger side). After changing, I couldn't tell the engine was running anymore, my idle was that smooth. So I sold the other mount on eBay for $40 about a month ago. Best 30 minutes and $30 I ever spent on any car ever. Period.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

Rahullio,

Cost me $359, which included installing new motor mounts and new transmission mount.

I do much of my work myself, but since my mechanic does yearly free checkup, takes us on short notice when we have emergencies, and does excellent work, I feel it is only reasonable to have some of the needed work done there.

Man, I wish I had the guts to lift an engine!

I don't even have a jack to lift the engine with....

What brand of jack do you have and how do you like it?
Is it available at Autozone or Pepboys?

The only thing the makes it reasonable paying someone to do the job for me is that all 3 mounts will be replaced... with 187,200 on the clock and no record of the mounts being replaced, I know they probably are way past due...

Have your idle RPMs increased in any way, I suspect not.... but maybe....

__________________
2006 BMW M5 "Heidi" @ 109,000 miles
2005 MBZ C55 AMG "Lorelai" @ 165,000 miles
1991 MBZ 300E "Benzachino II" @ 165,000 miles
1990 MBZ 500SL "Shoshanna" @ 118,000 miles

(On the hunt for a good used M103 engine as of 6/10/23, PM me if you have one to sell!)