Hi there and thanks for using just answer. I am AutoGuy99 and will be assisting you with your question. First i need to know if your service engine light is on? These engine have some normal issues that i will let you know about. They do tend to suffer from carbon build. up in the throttle body and intake. A good throttle body and fuel system clean can solve a lot of issues. Beyond that I would probably start by checking the EGR Valve (Exhaust Gas Recirculation Valve) to see if it might not be closing all the way. Sometimes the spring in the EGR Valve gets weak due to the excessive heat on the valve from the exhaust and if the valve gets dirty it will just partially close which feeds exhaust into the intake and makes the engine run rough. The exhaust gases upset the natural flow of the air/fuel mixture and usually makes a person think the engine is missing when in fact the air/fuel mixture to certain cylinders is diluted with exhaust
Check into these two things first. It also will not hurt to have a compression test and cylinder balance test performed on the engine.
That is good that the engine light is not on. This means all sensors are working correctly. Please check into the other things i suggested first and let me know.
Sorry if there was a delay in my response time. I always make an effort to respond as quickly as possible. My records show my last response on Wednesday at 10:20pm and then the next response was from you on friday at 10:46pm. There shows no communication between that time. What were the results of your compression test and cylinder balance test?
Well if the compression and cylinder balance test came back okay you don't have a problem with a bad cylinder. Have you checked into a bad harmonic balancer pulley or cracked flywheel. These will throw the engine off balance and give off vibrations.
Okay keep me posted
Mechanic says if those things were it, it would shimmy all the time and it doesn't.
If your mechanic has tried all the things i suggested then i do not have any more ideas. The issue with your car might require more of a hands on inspection. I will opt out of your questions so if any other experts have ideas they can assist you.