Shooting at the wheel from arm's length with his 12-gauge shotgun, he was peppered with buckshot and debris.
The man - who police say was on his own and not intoxicated - was taken to hospital with severe, but not life-threatening, injuries.
The man, from South Kitsap, 10 miles (16km) southwest of Seattle, had been repairing his Lincoln Continental for two weeks, according to the police, and had removed all but one of the nuts on the right rear wheel.
Frustrated by the one remaining nut which refused to budge, he resorted to fire power in an effort to shift it.
"He's bound and determined to get that lug nut off," said Deputy Scott Wilson, a spokesman from the sheriff's office.
He sustained injuries from his feet to the middle of his abdomen, with some pellets reaching as high as his chin, police said.
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