Ford engine controls manual page on Throttle Bypass Air, Idle Sp…

arm Electromc rumncummrwm Mm mm le Edit View Window Help I All @EQ-sEQ-i' ; lw l-+ leoleelm mt 4. THROTTLE BYPASS AIRIDLE ' ' Emm SPEED CONTROL (ISO) New E ConvertPDF les In Word or Excel anllne see. par rte lg m am We Controls vdf 'l 1 le / E7 38 MB The Throttle Bypass AirISO perlon'ns three iunctions: - Controls idle speed according to a variety of engine loads and conditions - Acts as an electronic dashpot during deceleration. preventing engine stalling. and preventing too~low manifold pressure that causes excess emissions . Provides additional air during starting. bypassing the closed throttle Convert Tu: Mirrusurt Wum (toned ' Remgnlze Text iii Englshtus.) Change Convert > create PDF > Send nus These roles are reflected in the new terminology under SAE J1930 in 1993, with the term ldleAlr Control." This throttle by- pass does more than most people realize since the functions of deceleration control and emission control are hidden by the name. I'm talking about the amoum of air that enters the en- gine when the driver's foot is oil the accelerator. In engineer log terms. an engine operating at no-load is at idle. regardless ol the rpm. 50 the name change helps us under. i stand this control. > Store nits Beginning with 1988 models. all Ford EEC systems use Idle Speed ControlByPass-Alr (ISC-BPA) Valve Assembly. ISC BPA bypasses air around the closed throttle plate(s). Although they are sometimes described by the same name. the EEC - ISC-BPA is quite dierent from the MECS~l ISO-EPA de- scribed below. The EEC unit uses only electronic control. while most MECS units use eoomblnation of electronic control and mechanical coolantcontrol. Exception: 1993 and later Probe 2.5L V4; idle air is controlled by Powertrain Control 9' - m"bWN'l'smmmmmm'sm .U .A __ ._ ..-,. L. , _-. ...- U... W. .-._. a..- a m throttle body to pmda a passage around lhml- .