xjs runs roughly at idle speed. help wanted

Hi, maybe you can help me. I own an XJS V12 (1988). Car is in very good conditions and has low milleage ( 80000 km, about 50k miles). I do live in the Canary Islands (Spain), so climate is mild (average temp

21ºC). This winter is a little bit colder (13ºC in the moorning). When I start the car in the moorning and it's cold (maybe hot for you...) it starts perfectly but at idle speed it varies roughly the rpm's (the engine does not stop but rpms go about 500 higher and lower than 800). It also makes a lot of smoke (@ both pipes) with a white colour (not a clear white but nearly a light grey to white smoke). After a few kilometres the idle speed becomes stable and the smoke dissapears (during driving, before it dissapears, if I drive at constant rpm's I can feel a light tendence to decrease/increase rpm's). I guess I changed the air filter, sparks, oil and oil filter one year ago. Can someone help me before I send my car to the garage?

thanks in advance

Reply to
swd
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Sounds like a vacuum leak; lean running. The smoke is never a helpful clue as it could truely be steam. the jerking is an indicator of running lean.

On the v12 the intake manifold works quite well unless somebody at somepoint removed it. If the intake manifold is not torqued in steps, using the right tightening order, these intakes will tend to leak.

Distributors have been a major problem on v12. Prone to allow water inside and damage the advance mechanism. Rotate the rotor with your hand and let go. It should quickly snap back and should have no slack/wobble when gently wiggled.

  1. Change your fuel filters.
  2. Check for loose, missing, or cracked hoses.
  3. Spray carb. cleaner around the mating surfaces of the intake system.
  4. Have fuel pressure regulator checked for proper idle and driving pressure.
  5. Have exhaust checked for back pressure 0-3 psi is ok, anything over that might mean a failing catalyst.
  6. Clean temp sender connectors.
  7. Check fuel injection amplifier.
  8. Look iside the distributor for water damage and possible advance mechanism issues.

Here is a great document to download from Jag Lovers. Every XJS owner needs one. It is a Word document I believe. I can convert it to a PDF file if you need so.

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Ciao, Blake

Reply to
Blake Dodson

thanks for your answer. I will check all these points.

"Blake Dodson" escribió en el mensaje news: snipped-for-privacy@z14g2000cwz.googlegroups.com...

Reply to
swd

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