My car has gone over 200,000 miles. It is well maintained but lately there have been some issues with the vehicle. I've noticed that the engine became a bit noisy and shaky. It usually happens when the temperatures are low. This also occurs while the car is not moving temporarily, like at the traffic light. After the car runs for some time, these issues subside. What should I do? Is this a serious problem?
It depends, it could be something as simple as carbon deposits in the throttle body disrupting cold start airflow to low/unbalanced engine compression on a cold start. Because the engine is well-maintained, the first thing to do is to have fault codes read out of the engine to ensure there are no underlying issues causing the rough running on a cold start. Then, the throttle body should be cleaned if it hasn’t been.
When an engine is started cold, the engine computer runs off preprogrammed values until the oxygen sensors come online. If there are carbon deposits present, this could change the actual airflow coming into the engine than what the computer expects, which could cause rough running.
If there are no faults present, and the throttle body cleaning does not correct the issue, then it may be caused from normal wear and tear based on the mileage of the engine.
An engine compression and leakdown test may need to be performed to see if there are combustion chamber issues that might warrant an engine overhaul. You may want to enlist the help of a mechanic, such as one from YourMechanic, who will have the tools and expertise necessary to diagnose and correct the shaking issue so that you can get back on the road safely.