James Wehr was pulled over by local cops just hours before his death … and we’ve now learned the reason why.

A spokesperson for the Newport Beach Police Department tells TMZ … on Saturday at 7:21 PM, an officer “observed a vehicle with a loud exhaust and conducted a traffic stop.”

We’re told the stop resulted in a warning issued to the driver, and he was sent on his way.

Just 5 hours later — shortly after midnight early Sunday morning — James’ 2019 McLaren crashed. He and the passenger, Alexis “Lexi” Kramer, were both killed.

James was married, and Lexi was not his wife. Lexi’s family says he hid the true nature of his marriage from Lexi … allegedly telling her he was getting a divorce.

We obtained video of the shocking crash … which shows James lose control of the car and crash into a tree … igniting a huge fireball.

Police are investigating the crash.