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Bad Idle When Pumping The Brakes

Legumis

By Legumis,
in General Maintenance

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Legumis Contributor

Legumis

Posted
Posted

my r33 has a slight pop when idling, which I've made my peace with. However, while sitting outside Nando's the otherday I noticed that I can bring on a much, much worse popping situation if I pump the brakes.

The more I pump the brake, the worse the popping gets to the point that I think its going to stall and I stop. The engine recovers after a few seconds to resume its "normal" idle shenannigans.

While inducing this over-pop, the revs seem to sit around normal warm-idle (650rpm for me) and don't drop.

Anyone know why this is? I have my suspicions about the electrical system, particularly in relation to the plugs and coils, but I'm a noob so, yeah.

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https://www.sau.com.au/forums/topic/215582-bad-idle-when-pumping-the-brakes/
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Godzilla32 Veteran

Godzilla32

Posted
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It will be the one-way valve that supplies the brake booster with vacuum. Normally it will only let air into the booster but if it fails, when you press the brake pedal the diaphram in the booster is actually pushing un-metered air back into the inlet manifold. The situation is leaning out the mixture and causing a slight rpm rise and the popping. If its the same as the 32 its located in a bracket on the master cylinder. Take it off and check if you can blow air (with your mouth) through either way. it will be marked as to which way its supposed to flow. PM me if you need a pic.

Deren

QWK32 Veteran

QWK32

Posted
Posted
If I can blow air against the flow direction, whats the fix? replacement?

go to the wreakers and get another one in working order. it shouldn't matter which model you get on from, eg. r32 r33 s13. as long as its working properly and the pipe fitting sizes are the same.

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