I Can't Believe How Smooth My Idle Is Now!!!

[gmercoleza]

1991 300E, 126,000 miles. Up until last night, the car had a rough idle. I mean REALLY rough. Stopped at a light with the trans in D, it would shake so bad that the hood would visibly jump around. The dash and something under the steering column would also rattle and occasionally emit this very loud, deep groan, sort of like a harmonic vibration that you could not stop. I thought something was loose under there. Sun visors and doors also produced rattling and rubbing noises. It was somewhat embarrassing whenever I had passengers.

I had been perplexed since the cap, rotor, wires, and plugs were all replaced about 3 months ago and the car passed the state emissions test with flying colors. I knew the engine wasn't misfiring or running poorly in any way. I figured the car was just really old and that things were just rattled loose from the 13 years and 126,000 miles of driving. In short, I began to just accept the rough idling as part of the character of the car. I recalled my last Mercedes, a 1986 560SEL, idled somewhat rough as well (although not quite as bad), so I reasoned that these German cars must just end up a little less refined in some way once they were past their prime.

I had been doing some research regarding the rough idle, and stumbled upon a few threads that talked about motor mounts. I saw a pair of them at a good price on eBay, so I decided to take a chance. Let me tell you, this is the biggest bang for the buck improvement I have ever done to any of the cars I have ever owned, hands down.

Most of the threads here indicated that only the passenger side mount usually needs to be replaced, so I only replaced that one. It was very easy and only took me about 30 minutes. Now, stopped at a light with the trans in D, it is smooth as glass. You can barely even tell the engine is running. Simply incredible!

If you have been struggling with a rough idle on your W124, stop what you are doing now and GO GET A MOTOR MOUNT! You won't regret it. Instead, you will be kicking yourself for not having done it sooner. In fact, if anybody here wants one, I will sell my other motor mount for $40 shipped. I paid $70 on eBay for the pair, but most likely you don't need two. The passenger side mount fails prematurely due to the heat from the exhaust manifold which is only a couple inches away. Mine had collapsed about 3/4 inch compared to the new one (I will post pics soon).

If anyone wants the motor mount for $40 shipped, please let me know. It will also work on a 201.