i have a 98 navigator 5.4, that has a low idle, it doesn't stall but in gear it hovers around 450-500 rpm in park or nuetral it is about 550. i changed the iac motor with a new one from ford but no difference. is there a way to bump up the idle, or any idea what might be wrong. thanks brian h

 

Clogged EGR will bring your idle down. Make sure all the lines running to it are in good shape but more than likely it's the valve itself.