My car was sitting for a week in cold weather. I started it yesterday with no problem, but only waited for a minute or two before driving. I was driving at city speeds, and heard a knock. I was accelerating up a hill and it hesitated/ jerked once or twice. The check engine light came on, and now it knocks every few seconds when I am stopped at a light. It also doesn’t seem to catch the highest gear (5?) when it shifts, making a constant knocking sound and vibrating. Letting go of the gas or accelerating so it shifts back down makes the noise go away. In other gears it seems fine, with an occasional jump… It is an Automatic V6 if that helps at all. I am taking the car in Monday, but I would like to know possible causes.
This morning I let my car warm up for 40 minutes (15 minutes in park and 25 idling at the bus stop). The problem was no better.
By knock I meant it feels like someone bumped the engine. My foot vibrates on the brake for a second.
And when it changes into the highest gear, it shudders ( until I release or further press the gas pedal. The revs don’t change while it is shuddering or knocking