Dating this Azure Blue Firemist Cadillac Coupe DeVille (EDIT: Looking more closely at the trim, this appears to actually be a ritzier Fleetwood Brougham Coupe) is made easy by the fender badge, which denotes that it had Caddy's V-4-6-8 engine.
While cylinder deactivation isn't especially uncommon now, it was pretty radical back in the days when really powerful computers still had their memory measured in kilobytes.
The 1980 Caddies had been using the 368 cubic inch L61 V-8, which was the older 425 cube motor with the bore reduced to 3.8 inches. The stroke was left at 4.06", which made for an undersquare tractor motor that got better gas mileage. It was fuel-injected on the front wheel drive Eldos and Sevilles, but the RWD bodies still used Rochester Quadrajet carbs.
For 1981, Cadillac added a complicated cylinder deactivation system that would use solenoids to lock the rocker arms on the deactivated cylinders, creating the 140bhp L62 V4-6-8. Now using throttle body injection on all models, it would theoretically use all eight cylinders for accelerating, six for normal around-town driving, and only fire on four cylinders for interstate cruising.
It was a public relations nightmare, received thirteen programming upgrades in its sole model year of retail sales, and would probably be remembered as the crappiest artifact of the Malaise Era if it weren't for the fact that Oldsmobile's 350 Rocket Diesel hadn't been an even bigger disaster.
Fortunately, the whole system could be disabled by disconnecting a single wire, which this one has almost certainly had done since the driver does not appear to be shedding tears of impotent rage.
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