Why do I need some throttle pressure to start an EFI engine? By opening the throttle are you telling the computer more gas or more air? Fuel delivery checks good, pressure with no bleed back. No codes other than 12. Runs well but an intermittent problem with the engine cutting out when removing throttle pressure to slow down.
Needs some throttle to start. on 1990 Chevrolet Celebrity
by olderndirt in Rochester, WA on May 26, 2011
ANSWER by dandd , May 26, 2011
If the idle air control motor is not working properly, you may need to open the throttle, it is not throttle pressure, you are just telling the computer to give more fuel AND air. If your engine dies out when coming to a stop sign at city driving speeds, then again you may have a worn out idle air control motor or a very dirty throttle body, a vacuum leak etc. If the car bucks and jerks and dies when slowing down from freeway speeds, then it may be a lockup torque converter problem. Throttle pressure by opening up the throttle valve is an input to the transmission so the upshifts are performed at higher speeds. This prevents the governor pressure from pushing the shift valves through the 1-2 and 2-3 etc etc cycle until higher road speeds, so you can get more power in each gear.