[xj-s] CYCLING idle at startup ...but a cold engine {Scanned}

Check your throttle bushings. Are they:

A) Missing?

B) Broken?

C) In perfect condition?

Write back.


Paul M. Novak

1990 XJ-S Classic Collection convertible
1984 XJ6 Vanden Plas
1969 E-Type Fixed Head Coupe
1957 MK VIII Saloon
Ramona, CA
@Paul_M_Novak1----- Original Message -----
From: “stephen sarmanian” s2steves@hotmail.com
To: xj-s@jag-lovers.org; “cardogs” kpaulwhite@hotmail.com
Sent: Wednesday, March 29, 2006 7:34 PM
Subject: Re: [xj-s] CYCLING idle at startup …but a cold engine {Scanned}

Sounds like a sticking Aux Air Valve beginning to fail (little fire
hydrant-looking device, top rear of water rail, B bank, readily
That’s how my symptoms began. If it’s the AAV it gets worse over time and
the cycling eventually appears during normal driving.

This subject comes up on the list frequently. Unless others suggest a more
plausible fault, look at the Book for a simple test while the engine is
idling, plus read the fix information. Check the Archives for additional
experience (like: don’t break the screws, use washers beneath them, buy a
gasket, replace the top 1" elbow hose). There are a few postings under my
name, other listers have been more creative with their fixes and have
contributed more by the way of photos and articles on jag-lovers. There
three levels of fix:

  • clean then test the AAV in a pan of boiling water as you would any
    similar thermostatic device, squeeze the bulb or tap it upwards to get
    proper travel per the Book (cost of the gasket is maybe $2 USD, moderate

  • replace the bulb with a direct rebuild kit (maybe $100 USD) or
    an adaptation
    of another bulb (minimal cost, lot of labor).

  • or, buy a new AAV (maybe $350 USD), a waste of money in my opinion.

See what others have to say.

Steve S.
Lexington, MA USA
'91 xj-s v12 coupe

----- Original Message -----
From: “cardogs” kpaulwhite@hotmail.com
To: xj-s@jag-lovers.org
Sent: Wednesday, March 29, 2006 7:50 PM
Subject: [xj-s] CYCLING idle at startup …but a cold engine

1991 5.3 v12 startup idle cycles between abt 500 and 1400 rpm
until I moderate it with the accelerator, car warms up a
little bit and all is well. the car does this only

// please trim quoted text to context only