What Could Cause A 2000 Chrysler LHS Shaking?

I bought a 2000 Chrysler LHS. It has very high miles, 216xxx. When I was leaving work, the engine light popped on and the car is shaking. I took it to autozone to see why the engine light came on, the guy told me it needs a tune up because cylinder 5 misfire. So, I bought the spark plugs. Still misfire. And now,... show more I bought a 2000 Chrysler LHS. It has very high miles, 216xxx. When I was leaving work, the engine light popped on and the car is shaking. I took it to autozone to see why the engine light came on, the guy told me it needs a tune up because cylinder 5 misfire. So, I bought the spark plugs. Still misfire. And now, its shaking badly. If I do 35 or more, it jerks like the engine is going to give out. So, I changed the coil pack on cylinder 5. After changing, it shook while accelerating. It shakes very bad while in parked or reversing and it feels like the engine will die. What could be causing this problem? The coil packs and spark plugs are changed and the computer isn't telling me what else could be wrong. It keeps saying cylinder 5 is misfired when it was changed and dealt with.
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