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Old 08-05-2019, 06:58 PM   #1
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Throttle body cleaning and associated vacuum hoses location

vintage 1997 Boxster....

Shortly after I changed the oil, the revolutions at idle began to oscillate between 300 rpm to about 1200 rpm. Reading various forums identified the most common problem is a dirty throttle body, possibly the Oil Air Separator (OAS). Given the car has 34K miles and cleaning the TB has never been done, I figured it was time. The throttle body was indeed filthy with a very light oil-like coating, and same for the plenum to the cylinders. Having seen pictures of the effects of a bad oil separator, I figured mine was ok and what I observed was just buildup of 34K miles.

After a through cleaning I reassembled the TB and remounted it (what a PITA that was because each side of the 'T' plenum would not line up with their respective intake manifold). What a struggle.

Finally got it beat into submission and connected the vacuum lines and this is where I need some help. Standing behind the engine, on the extreme RHS there is a vacuum line with what looks like a check valve that goes into the RHS plenum. Got that inserted although is seems rather loose.

Now, on the LHS at the rear, when I had removed the TB, I noticed a very small (less the 1/8" OD), thin black hose about 6" long that was adjacent to the hydraulic fluid reservoir - I don't recall if I pulled this out of the 'T' plenum or where is should be plugged.

Can anyone offer any suggestions? Perhaps a drawing showing the vacuum lines attached the the TB plenum?

The car seems to run OK after the cleaning and I do not notice any strange behavior.

Insight much appreciated.


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Old 08-12-2019, 12:18 PM   #2
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Old 08-12-2019, 12:21 PM   #3
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These links may help. There is a small diameter vacuum hose that plugs into the front of the T on the driver's side and goes to the fuel pressure regulator in front of the airbox behind the drivers seat. Give that a check.

air intake/vacuum line routing - Pelican Parts Forums


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