“TONIGHT SHOW” host Jay Leno found his dream car behind the sealed doors of an old garage that hadn’t been opened in years . . . and it was a doozy.

Actually, it was a “Duesie” — a classic 1920s Duesenberg that was parked there in 1947 . . . and hadn’t been moved since.

In an exclusive ENQUIRER interview, the hard-driving star revealed how he played Sherlock Holmes to find the vehicle — and then got a stubborn owner to sell it.

“It was kind of like playing ‘car detective,’ ” said the funnyman — who owns some 80 classic vehicles.

Jay shifted into high gear after hearing “through the grapevine” that an old-timer had a vintage vehicle hidden in a Burbank, Calif., garage. “I knew that there was a car in there — or possibly even two,” Jay told The ENQUIRER.

“They were rumored to be Duesenbergs — but no one had actually seen them.”

The car-loving comic made several trips to the garage, but couldn’t convince the owner to let him have a look inside. “He’d always come up with some excuse as to why he wouldn’t open his garage for me. This went on for some time.

“Then in 1994 we had an earthquake. The garage shifted, the door got stuck, and now he had the perfect excuse not to open the garage . . . because he couldn’t!

“Finally, I’d heard the old man was put in a nursing home so I spoke with his daughter.”

Jay negotiated with the woman and her dad to let him look inside the garage.

When he finally got the door open, he was stunned to see a 1927 Model X Duesenberg sedan in great condition — one of only about 13 built!

It hadn’t been touched since 1947 — and neither had the garage, apparently.

Near the vehicle were stacks of newspapers with such headlines as “Japan Attacks Again!” Jay purchased the prized vehicle, and began making it roadworthy.

Generous Jay believes so strongly in the importance of preserving vintage cars as part of our heritage that he has set up scholarships for youngsters who want to become expert mechanics and car restorers.

“This is quickly becoming a lost art,” he explains, “and I don’t want to see that happen.”