If it diesels you probably have the butterfly open too far at idle.
Back off on the stop screw a little bit at a time and alternately adjust the idle mixture screw.
Air flow through the throttle bore is what draws the fuel into the intake. You need to minimize it at idle.
The pistons are also most likely carboned up , creating hot spots to ignite the incoming air/fuel after the ignition is shut off. Get the engine hot and run some Seafoam into the intake.
Alternatively , what we old timers did was take a spray bottle with ice cold water. Get the engine hot then open the butterfly wide open for a second and spray a shot of water in the carb at the same time.Don't hold the throttle open just let it snap back right after you spray.Wait ten seconds,repeat.Do that 5-6 times.
The cold water hitting the hot carbon deposits makes the carbon shatter and blow out the exhaust.
Don't be surprised if the engine runs a little rough right after.Sometimes a chunk of carbon will get wedged into an exhaust valve ,holding it open slightly.It will work it's way out.
Archimedes screwed us !
I knew a blonde dyslexic agnostic insomniac - she'd lay awake at night, wondering if there really was a Dog.
2003 Ranger Edge 3.0 manual 2WD