The instructions leave a lot to be desired, so let me share with you what I figured out through trial and error. Hold the [space] bar and release it when the throttle in the lower right is as close to max as possible, to get an initial boost of speed. Then, hit [space] again when you want to turn on the engine. As a note of strategy, while high speed makes you travel over more ground, lower speed makes it easier to make sure you steer into the obstacles. Then, steer with the [up] and [down] arrow keys. If you've purchased additional tools such as a gas can or a grand piano, switch among them with the [left] and [right] arrow keys, and select one by using [space].
For the objects like the grand piano that you drop on your head, hit the [space] bar once, and then again when the object is directly over the car. If you hold the button too long, the object will bounce harmlessly in front of you, which is probably the most frustrating aspect of the game.
A serious drawback to the game is that doesn't appear to be any way to save. If you want to kiss that bunny, you had better be prepared to do it in one sitting. But the game shouldn't take that long to complete. As for the aesthetics of the game, they're probably where it shines the most. The zany music, art, and the main character combine for a No-Intellectual-Property-Was-Harmed version of Bugs Bunny. The entire game is a spree through that kind of Loony Tunes logic where you can smash at top speed into a giant weight (helpfully labeled five tons), merely have some comical bandages and a swirl of smoke over your head in the next scene, and in the scene after that be perfectly fine.