A naked woman and man with his pants down were found dead in a car in a Queens garage yesterday, the apparent victims of accidental carbon monoxide poisoning, witnesses and an FDNY source said.

Jonathan Tapia, 21, and Delly Collado, 28, had been dating for a short while and lived with their families a few blocks apart.

"We smelled fumes on the first and second floors," said Luis Padilla, who rented the garage attached to his 99th St., Corona, home to Tapia. "I opened the garage and discovered the bodies. They were nude."

One of Padilla's relatives tapped on the window of the Acura about 7:30 a.m., but the couple, motionless in the front passenger seat, didn't respond. The engine was still running, the likely source of the deadly gas.

By coincidence, one of Tapia's cousins, who was expecting a ride to work, grabbed a spare key and went to the garage. He opened the car and found the bodies cold to the touch, witnesses said.

An ambulance was called but nothing could be done.

It's not clear how long the couple had been in the car, but experts say carbon monoxide, a colorless and odorless gas, can kill within six to eight hours of continuous exposure.

The medical examiner's office has scheduled an autopsy for today. Police said there were no signs of trauma to the bodies.

Two people from Padilla's house were taken to Elmhurst Hospital Center for treatment of exposure to the gas.

Tapia, a Queensborough Community College student, lived a few doors down from the garage with his mother, stepfather and sister, relatives said.

"It's something you don't expect," said Wilson Vera, 30, the dead man's uncle. "I talked with him yesterday, and today he's dead."

Tapia, of Ecuadoran descent, worked at a carpet business.

Collado, of Dominican heritage, loved fashion and took classes at the Katherine Gibbs School on W. 40th St. in midtown. She lived with her mother and at least two other siblings, a neighbor said, just a few blocks from where she died.

"We think it's a tragic accident," said her brother, Ramon Collado, 30. "She was a good kid. She was into art. She loved to draw."

The couple's relatives shook off any thoughts of a suicide pact, saying both had every reason to live.