The vehicle needs to be in US for at least 72 hours beofre you import it to Canada after you report to US custom. Say, you are going to land in Canada on 9/1, and you'll going to import the car same time you land in. You need to fax your vehicle title to US custom on 8/29. On the way you drive to Canada, you'll need to stop by US custom, and tell them you faxed your vehicle title on 8/29, they'll look into the fax docs, after they find your vehicle title, they'll stamp on your original title to prove this vehicle is export to Canada. When you land in Canada, you'll need to go to Immigration Canada first, then they'll ask you whether you have any goods to import. Tell them you have vehicle, they'll let you show the title. If you don't have the seal, you'll not able to import the car at same time when you land in. You'll have to go back to US custom, show them your title, and hold the car in US custom for 72 hours, then come back to the border to pick up the car. Very complicated.
SO the best solution is to fax your vehicle title to US custom 72 before you head to Canada. You'll also need to decide which port you'll going to land so that you can find US custom's phone number. One more suggestion, if your car is old, you'll suggest you buy a new car to import. The sale's tax and vehicle price are extremely high in Canada. It is not worthy to import an old car to Canada. While you have free duty when you land in Canada.