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1985 Alfa Romeo Spider 2.0 Graduate
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Discussion Starter · #1 ·
Working on replacing vacuum hoses today, which based on the cracked ends it’s probably a decade overdue…this one connection on the plenum, the upper in the photo doesn’t seem right being loose and rotating. need to upload a video but thought some might be able to comment.
Wood Gas Auto part Plumbing Machine

Before I start fighting with it, I wanted to check if this is ‘normal’. Appreciate any suggestions…
 

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That's pretty normal.

If you take it apart you will find a small o-ring at the bottom. That o-ring compresses as you tighten the upper nut which in turn adjusts your Idle speed. The lower nut is to lock it in place once idle speed is set but the pipe you see there will still rotate freely (at least it does on my car).

If you haven't already, you might want to download and check out the L-Jet diagnostics page in the following link:


Good luck.
 

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Premium Member
1985 Alfa Romeo Spider 2.0 Graduate
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58 Posts
Discussion Starter · #4 ·
That's pretty normal.

If you take it apart you will find a small o-ring at the bottom. That o-ring compresses as you tighten the upper nut which in turn adjusts your Idle speed. The lower nut is to lock it in place once idle speed is set but the pipe you see there will still rotate freely (at least it does on my car).

If you haven't already, you might want to download and check out the L-Jet diagnostics page in the following link:


Good luck.
Thank you. I got the vacuum hose kit from HPSI and will be following their tuneup guide.
 

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Does anyone stock those O-rings?
There is nothing magical about that O-ring. Take the old one to the plumbing section of a hardware store and find one about the same size. (I don't recall the size offhand.)

When they're new the O-ring is compressible - the idle speed adjuster can compress it to vary the ID and thus the amount of air it'll pass. When they get old they get hard and turning the adjustment nut no longer makes the ID change.
 

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I had trouble finding one at my local hardware stores so I reached out to Jon at Alfa Parts in Berkeley and he had them in stock. That was a year or so back but I'd give him a ring
 
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