Idle is 1800-2000 RPM ??? - Alfa Romeo Bulletin Board & Forums
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post #1 of 4 (permalink) Old 08-07-2019, 01:52 PM Thread Starter
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Idle is 1800-2000 RPM ???

I’ve been driving my 1988 Quad and enjoying it since I did all of the fuel lines and some other repairs. Car runs good but Idles 1800-2000 rpm. Is there a way to adjust this or am I opening a can of worms.

Anthony "Yac" Yacopino
Finger Lakes Region NY
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post #2 of 4 (permalink) Old 08-07-2019, 02:58 PM
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First check the idle speed with a known accurate tach (many timing lights also have a tach function). The Alfa tach is not known for its accuracy.

The normal idle speed is about 950 +/- 50 rpm. There is an idle air adjuster on the intake plenum. Inside is a rubber O-ring. Squeezing or unsqueezing the O-ring by using the idle air adjuster varies the idle speed by varying the ID of the O-ring. But when that O-ring gets old it gets hard and often won't change its size. The simple solution is to take the adjuster apart and replace the O-ring. I just took my old one to the plumbing section at the hardware store and got one about the same size.

There is also a throttle stop screw on the intake. But that is not meant to be fiddled with - of course that doesn't stop the unknowing from messing with it. The throttle stop screw should be set to almost allow the throttle plate to fully close but not so far as to stick closed. If I find one messed with, I back it out then slowly turn it in until the idle speed raises up about 50 rpm from fully closed (thus you need an accurate tach for this). Then set the correct idle speed with the idle air adjuster.

Finally, the AAV (Aux Air Valve) is supposed to open when cold to raise the cold idle speed and shut when warm. But they often fail half open. Check the AAV - if it is open when warm that will also raise the idle speed. There is info in the Spider FAQ thread about installing a manual AAV.
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~ 1984 Spider Veloce ~
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post #3 of 4 (permalink) Old 08-07-2019, 03:08 PM
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One other thing to check is the throttle position switch (TPS) on the side of the throttle. If it is mounted in the incorrect position, it can result in a high idle.


'85 Spider Veloce
'17 Giulia Ti Sport
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post #4 of 4 (permalink) Old 08-07-2019, 06:38 PM
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The distance between the end sockets on the two rods that make up the throttle linkage is adjustable. Both rods have threaded ends that the ball sockets screw onto, and the horizontal rod (located under the plenum) has a turnbuckle to adjust the length. If these ball socket ends are screwed too far onto the rods, or the turnbuckle has shortened the length of the horizontal rod, the throttle plate will not rest on the throttle stop screw. This problem can also be caused by worn motor mounts which let the engine sit too low and pull the throttle linkage out of adjustment.
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