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Misfire/vacuum issue

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Regarding a Boxster S from 2000

Short story, for a about a week i have heard a hissing sound from time to time while driving.

And also when i turned of the car there was a sound as letting out pressure.

Now i have been away for 2 weeks and when i start my Baby she sound like a V8.

The whole car shakes ALOT when i give som gas but if i stay at a stable rpm for it tends to shake less.


So i bought a cheap OBD2 reader today and found misfire issues on all the cylinders wich tells me that it could be that the hissing sound and this is reletated.

stupid me deleted the codes and the third time i started her up she runs without the misfire but there aint the same "kick" in her.

I opened the hood and found the source/leak, its the tube i Point at.

My question is, what is that tube and can i fix it myself?

Its the gray coupling that leaks.



Thanks in advance :)

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The tube that you indicates go to the brake booster in the front trunk, the valve is a one way valve. Check where the leak is properly located in first place, the tube or the valve.

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Thanks RFM!!


So this would realy not give me any problems as misfire and and newbie question, what does the brake booster do? :blush:

The gas tank was nearly empty when i was away so to rule out condensation i filled here up after the engine started to run better.

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The answer is yes, it can cause a lean misfire as it is leaking outside air directly into the intake manifold.

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