I have a 1994 f150 with a 5.0 L and a manual trans. my question is when I am rolling down A hill or coming to a stop about two or three seconds after i take my foot off of the accelerator the truck feels like I have taken it out of gear there is no engine drag slowing the truck down. I feel this is normal operation because my old 1991 f150 did the same thing and it was an auto trans. what type of engine function is this ? can someone explain.