Hello,
I have an 88 mercedes 560sec. When I start the car it shakes VERY badly until it gets warmed up, once its warmed up it seems to run pretty good though. It is not just a vibration, the whole car shakes. I'm thinking that it is an injector. But I've read many things on here about different things. Oh and I've been driving the car like this ( I know It's probably bad) and it hasn't got any worse. Let me know what you think it is and how much to get fixed. Thanks for any and all advice.

Could be as simple as a bad plug wire resistor.

One of the differences between a warm and cold engine is idle speed. A higher idle speed will place more torque on the engine mounts when in gear, showing up a collapsed mount. If the shaking seems much worse in gear than in neutral, that is what I would suspect. If the shaking continues with a cold engine that has dropped to low idle, but not when fully warm, then the engine mounts are less likely than a fuel supply or ignition problem.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

The shaking stays the same when in drive or park, The tachometer is not jumpy. That is where I'm confused, it could be spark plugs, wires, injector, the motor mount or who knows what else. Thanks for the help