1996 Ford F150 Owner's Manual - Page 60

A computer system controls the engine's idle speed. When you start your vehicle, the engine's idle speed normally runs higher than when it's warmed up. These faster engine speeds will make your vehicle move slightly faster than its normal idle speed. It should, however, slow down after a short time. If it does not, have the idle speed checked. If the engine idle speed does not slow down automatically, do not allow your vehicle to idle for more than 10 minutes. Have the vehicle checked. RWARNING Extended idling at high engine speeds can produce very high temperatures in the engine and exhaust system, creating the risk of fire or other damage. RWARNING Do not park, idle, or drive your vehicle in dry grass or other dry ground cover. The emission system heats up the engine compartment and exhaust system, which can start a fire. If you consistently start your vehicle in subzero temperatures, use an engine block heater (if your vehicle has this option). Engine Block Heater (If equipped) (Standard in Canada) Engine block heaters are strongly recommended if you live in a region where temperatures reach -10˚F (-23˚C) or below. An engine block heater warms the engine coolant, which improves starting, warms up the engine faster, and allows the heater-defrost system to respond quickly. 58