When I am driving about 40 in 5th gear and let off the throttle, there is a slight jerk in the engine. Is it a loose motor mount?
Very well could be broken engine mount. Is the engine smooth as far as tach when you let off the gas? Could be a transmission issue with the lockup torque converter. Is it an automatic? What is the year and mileage?
It would be a great help to know the year, make, model, engine, transmission (auto or manual), and mileage of the vehicle. As well as whether the vehicle is new to you, and if not whether the symptom is new or not.
Could be. But there are other possibilities. When you let off the throttle the fuel injection system usually shuts completely off (to save on gas). The transition can be more abrupt than normal if the idle speed is too high or there’s a problem with the throttle position sensor. Usually this is noticed as at lower speed too. And usually there is another abrupt transition when the speed slows enough that the fuel injection starts working again. It’s something to consider at least.
Its a 1999 civic hx, and its a manual 5-speed. It only does it in 4 or 5 gear going about 40-50mph. Its pretty subtle, but i’m not sure if i should be worried or not.
Any other ideas