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intake pressure lowers on light throttle

  • BrunoPecego
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3 years 2 months ago #57662 by BrunoPecego
intake pressure lowers on light throttle was created by BrunoPecego
1997 s10 4.3 MAP at around 29kpa at idle. For some reason if i apply just a little bit of throttle the intake pressure drops to about 25kpa instead of rising. If i continue to raise RPM, only then pressure starts climbing above 30kpa. Bad MAP sensor?

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  • juergen.scholl
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3 years 2 months ago #57663 by juergen.scholl
Replied by juergen.scholl on topic intake pressure lowers on light throttle
This is a normal condition and no problem at all.

Under light acceleration the throttle plate is maintained in a still almost closed position so the higher rpm will create a stronger suction = higher vacuum within the intake manifold. It is not until higher loads demand a substantial opening of the throttle plate when the intake manifold vacuum starts to drop until it eventually catches up with barometric pressure.
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