High Revs at a COLD start on 1989 XJS V12
 

I have a 1989 Jaguar XJS with the V12 engine. It runs great but on startup with a COLD engine the revs go up to 2000 rpm or so and then after a few minutes calms down to a regular idle when warm. What are the issues here as I hate to start a cold engine and then see it go to high RPM. New member. Michael W. Jacobs

Welcome to the forum Michael,

I've moved your question from USA - Northwest Region to XJS forum. This is the place to post technical questions about your vehicle and members here with the same model will be able to help.

When you get a minute, please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST forum and post some info about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham

yeah 2000 sounds a bit high, but remember engines are designed to rev up when cold so they warm up a bit faster and run properly, its like an automatic choke.

What is your warm idle at??

I would probably suspect the AAV, keep in the mind the adjustment screw on it is for the regular hot idle, and if there is an issue with the cold/fast idle in the AAV, it is a separate part of that assembly, either the heat sensing bulb or the piston itself.

To make sure the AAV is the problem, remove the left side air filter cover and element, start the car and let it warm up,
and check how much air is entering the hole where this valve is connected. You might even try covering the hole
entirely; since the warm idle air also goes through this opening, the engine RPM should fall to below a normal warm idle
or even stall, although it will be sucking air through the distributor vent scheme like crazy. If the idle drops a little but
remains high, your idle speed problems are probably due to something other than the AAV.(Palm 265)