Those units are notorious for having that problem due to heavy emissions and a light aluminum transmision casing. First check ignition system cap ,plugs, wires ect. Then remove the throttle body and clean the throttle plate and housing (they always have lp gum on plate and housing). check timing to mke sure it hasnt been tampered with. Remove the right foot pedal step and you will see a small plate,remove and there will be a **** for idle adjustment. adjust but dont max out it will throw a engine code when trying to start. then the lp regulator has a metal cap on top that can be knocked out. that will give you a little more low idle adjustment. hope fully this will help good luck