Q: Poor acceleration

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My car runs smooth at idle and at steady speed but when accelerating, it shudders. Sometimes it is less noticeable when fully warmed up. In addition, I get a faint scent of anti freeze. There is no obvious signs of anti freeze leaks.

My mechanic can't find the problem.

Bob

My car has 122000 miles.
My car has an automatic transmission.

If your car has not had a major service that has involved replacing spark plugs and all the filters that might be all that you need. Mercedes recommends replacing the plugs at 100 k but I prefer to do it more often (about 60 K) just to prevent having them seize up in the head. When under acceleration, the resistance in the combustion chambers is at it’s highest, so any ignition fault will show up then. I’m more concerned about the smell of anti freeze. You may have a small leak in the system or you might even have a leak in the heater core which is why you smell it inside. I don’t believe you would be smelling it if it was coming out of the exhaust while you are moving. Your should be sure to have that checked out as well. You can have these things done at your home or office by contacting You can have these things done at your home or office by contacting Your Mechanic Be sure to mention the Coolant Leak as well.

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