As Dave Faircloth suggests, the AAV (Auxiliary Air Valve), also known
as the Extra Air Valve, is the most likely problem here, but anything
that allows air to enter the intake manifold, such as a vacuum leak,
can cause a high idle. Here is a diagram of the AAV (item 6) and its
connections:
http://www.jdht.com/webapp/wcs/stores/servlet/CategoryDisplay?catalogId=10051&storeId=10051&categoryId=20262&langId=-1&parent_category_rn=20260&top_category=20260
The black rubber L-shaped hose (#4) connects to the back plate of the
left or B bank air cleaner. One test to see if you have some other air
leak is to remove the left air cleaner cover and element, and plug the
port in the air cleaner to which this AAV intake hose connects while
the car is idling. If you have no other air leaks the idle speed
should drop to ~200-300 RPM (yes, it will still run that slow).
The function of the AAV is described in Kirby’s Book. Generally, it
allows additional air to enter the intake manifold, either (1) by the
adjustable idle speed screw, 13mm screw on the AAV air intake (which is
NOT identified by name or number in the linked diagram above, but the
hole for the screw is shown beneath the AAV air intake), or by (2) a
changeable orifice which increases when engine temperature is cold, to
allow more air (similar to choke function in a carburetted engine), but
this opening should close as the engine warms.
Try that and let us know what you find.
George Balthrop, Clifton, VA USA
85 & 89 XJ-S Coupes; 89 XJ40 VDP-----Original Message-----
From: Got V12 bb4re1@yahoo.com
To: xj-s@jag-lovers.org
Sent: Fri, 22 Feb 2008 7:52 am
Subject: [xj-s] high idle 86 V12
I just purchased my first XJS. Very good condition, with 68K
California miles, but needs a little sorting out, nonetheless. Once
the car is warmed up I have an idle of around 1500rpms. Cannot seem
to get it down. Any ideas?
1986 XJS
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