Actually, we can take a scientific look at this.
The DeLorean was covered with ice only three times throughout the trilogy. First, when Einstein "tested" it. Second, when Marty first traveled to 1955, and at the end of the 1st movie, when he rearrives in 1985. Now, throughout these trips, the time machine used plutonium to fuel the flux capacitor, hencefore, time travel is possible. After Marty's first trip back to 1985, Doc install a "Mr. Fusion" to the DeLorean, and the car never ices up again. The ice and white smoke never appears again, therefore, it's possible it might have been a chemical reaction to the plutonium, or in the final case, the plutonium chamber being struck by lightning.
Pretty heavy, huh?
The DeLorean only gets icy when it goes into the future, not into the past. If you'll notice, at the end of the film, when Marty gets back to 1985, the time machine is icy. He even gives a loud "Whoo!" from touching the freezing car.
I don't remember where I read this, but I do remember reading somewhere that *if* time travel were possible, notable heat changes would be a likely side-effect of the travel. I don't remember which direction would get hotter and which colder, but I always figured that this was the cause of the DeLorean icing up - and for the fiery tire tracks.
That being said, I'd say it was a slip-up whenever either of these did not fit the already-established pattern (Ice going forward and fire going backward).
But now that I think of it, doesn't the show have it that the fire is left behind the car and the ice goes with the car?
erin, you said the only time you say the car leave behind fire was the lightning. but what about the beginning when einstein does it? marty and doc were standing on the fire.
and to the guy who said that it never blew smoke after the first time, im not quite sure, but me and my older bro were talking about today after we watched it and we decided it was a side effect of the first time travel ever on the car.
I agree with the theory that the Delorean only ices up when it goes to the future. Maybe it's just a 'MOVIE' device used to emphasize the epic journey through the fabric of time!! ( or perhaps Mr Zemeckis just wanted ice on the car???)
im not positive but im pretty sure it happens again in BTTF 2 when they go back to 1955 to get the alminac. when they park the car behind the billboard you see stuff on the car again. i think. i guess i should check before i post..oh well.
Actually, Not to knock Chris's theory, if you look in BTTF 3, after he's returned back to 1985 (via the train tracks) you can clearly see that there is ice on the DeLorean as he rolls past the intersection
Actually, here is another spec on the icing. If you were to read up on the DeLorean, it is a known fact that when the car ices up, the doors won't open at all. This is one of the down sides to purchasing the car. How the heck did Marty and Einstein get out if this is a proven case?
The delorean at the end of BTTF 1 is in fact icey when Doc returns from the future. At this time the delorean does have Mr. Fusion so it made no difference. Also the delorean is icey again at the end of BTTF 3 suggesting that it only gets icey when traveling to 1985!
I think there is a heat displacement-the delorean heats up due to air friction, but then when the temporal displacement occurs, the heat energy is left behind in whatever time the time machine was in before the temporal displacement and when the time machine returns, it has none of tha heat energy that was produced, so it freezes the air on immediate contact. Wow! I sound like a geek! In other words: (DeLorean+88mph=HEAT+Temporal displacement)(Temporal Displacement=Heat escapes)(DeLorean returns=No heat=ICY CAR!) I don't know why the car is Icy sometimes and sometimes not, though. I hope This helps you!