Why does your 1999 Toyota RAV4 sputter while idling in drive?

A 1999 Toyota RAV4 may sputter while idling in drive due to several potential issues, such as a dirty or faulty fuel injector, a clogged air filter, or problems with the ignition system, like worn spark plugs or ignition coils. Additionally, a vacuum leak or issues with the idle air control valve could disrupt the air-fuel mixture, causing rough idling. Regular maintenance and diagnostics can help identify and resolve the underlying problem.