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I am experiencing delayed forward movement at take off. I apply the accelerator nothing happens until it jolts forward. When I stop it lunges forward, which leads me to believe it is the motor mounts. However, I was told they were still good. I have recently changed my transmission mount to no improvement.

I have a 1997 Mercedes C230

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Sounds like you need to look at the rear bushing of the front wheel control arms. These are made of rubber on most cars and don't last beyond 100k. The thunk you feel is because a normal bushing has firm hold of the connection with the control arm, where as your control arm is probably loosely held in place by worn rubber. When you accelerate, the forces normally transmitted to the wheel to get the car rolling must first settle into the loose bushing cavity, sometimes quite violently, creating the thunk you feel or a lack of immediate acceleration. It will also thunk when you come to a stop, since the stopping forces that hold the control arm firmly in the loose cavity will be gone when stopped, so the control arm will re settle . It will only get worse and make your cars handling unsafe.

  • I think you are right. I have already ordered this part and have yet to install them. – James Sheridan Apr 28 '15 at 17:24
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This would not be a motor mount issue. What you are describing seems to be an issue with the transmission. IIRC, the C230 is a rear wheel drive vehicle. Only a front wheel drive vehicle would produce anything like what you are talking about with bad motor mounts, but then it will be far less noticeable. A motor mount problem will not create the jolt like what you are talking about, but rather a thump when releasing the gas pedal (relieving torque from the engine), plus you'll get a lot of harsh vibration during operation. Even with a broke motor mount, you'll still get power to the ground.

Other than visually inspecting the motor mounts, the only way I am aware of to test a motor mount is to power brake the vehicle. What I mean is, while you are sitting in the driver's seat, apply the brakes tightly, put the vehicle into drive, and start applying power. While you are doing this, a second person is needed to view the engine (so you must have the hood open). What the second person is looking for is if the engine lifts off of its mount. It would be a definite movement and not just a slight torque over (I'm talking inch(es), not millimeters of movement). You'd also need to do the same thing in reverse to check the other side. Usually, the side which lifts when in drive will be affected far earlier than the other side as it takes a lot more abuse. You can utilize the parking brake on top of normal braking to perform this test. Please be careful in your surroundings. Do this in a place where, if the brake should slip, you won't run into anything. Ensure your assistant is off to the side of the vehicle and not in front of it.

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