Q: Car violently shakes at 30+ mph after cold start

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My car started violently shaking at low speeds 30-40 mph. It shakes REALLY bad. It feels like a tire is about to fall off or the engine is throwing itself around in the compartment. This only happens in the morning on my way to work but not on my way home. Also if I accelerate really quick it doesnt shake. I checked my shocks, axles and steering components for issues. Nothing looks bad. Havent checked my brakes or rotors though but thats my next thing. This started after I ran smoke through my brake master cylinder vacuum line trying to find a vacuum leak. I drove it after that and it was fine, then a couple hours later I started drive it would shake. It still shakes when Im braking. I have no reason to suspect my tranni because gear changes dont stop the shaking but I dont know. It has 2 bad engine mounts but those have been bad for 2 years and never an issue.

Any idea what the problem could be? What I can try to get it to stop? Should I stop driving it until what it is gets fixed?

My car has 170000 miles.
My car has an automatic transmission.

Hi Chris. Thanks for writing in tonight. The biggest problem with bad motor mounts is that when they fail, they tend to fail rapidly; so that might be what has happened to your Mitsubishi. However, it’s also possible (although less likely) that the wheel bearings are the source of your problem, or as you tested for earlier, you’ve got a pretty aggressive vacuum leak. It is also possible that an electrical connection to an ignition system or fuel injector might be loose, which can also cause an aggressive vibration. To be honest, there are about a dozen more possibilities, which is why it’s always best to have a professional mechanic come to your location and complete an onsite inspection as soon as possible. I would strongly recommend not continuing to drive the vehicle, as this type of problem can morph into more severe repairs.

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