Why wont a 1990 Nissan 240sx will run but not stay running?

A 1990 Nissan 240SX that starts but won't stay running could have several issues. Common causes include fuel delivery problems, such as a clogged fuel filter or failing fuel pump, or ignition system issues like faulty spark plugs or ignition coils. Additionally, vacuum leaks or a malfunctioning mass airflow sensor can disrupt the air-fuel mixture, leading to stalling. It's best to perform a diagnostic check to pinpoint the exact problem.