If the desired engine is inside a car:
1.grab the car using capital G+Direction
2.Move it to your workshop or your other vehicle.
3.Un grab the car and take its engine
4.Use the engine where you wanted to.
If the engine is not inside a car, then just pick it up on your hands and go to your destination, ignoring any monsters or pain (if you have a light vehicle with storage space near you, then put the engine there)