XJ6 & XJ12 Series I, II & III 1968-1992

1985 XJ6 3.4 Series 3 Starting / choke problem

Old 05-19-2008, 05:49 PM
Jose's Avatar
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Default RE: 1985 XJ6 3.4 Series 3 Starting / choke problem

I will throw some hints at you but I am not a Technician, instead I am a TAENICIAN, a Trial And Error Nician.

I have 17 years experience with my '84 and you could say I've "been there, and done most of that". I amfamiliar with the 4.2 fuel injected engine, and withthe 3.8 carburetted engine.

In the XJ-6, the "hunting" (up and down) of rpm's when cold, is usually the classic symptom of a sticking Auxiliary Air Valve (AAV), which of course, un-sticks itself after the engine is warm, just like your pain dissappears as soon as you getto the doctor's office.

Another related component, but not necesarily the culprit in your case, it's the Cold Start Injector dripping fuel when it should shut itself off. But I assume your car does not have the CSI, since you say you have a "manual choke".

Isuspect it's the AAV.The attached picture shows the AAV to the left of the red arrow head. Removal is not easy, and even then, cleaning it is another story in itself, I hope you have a Factory Shop Manual and a new gasket for reassembly. (not a Haynes manual, those are useless for the XJ-6).

Otherwise I'm sure someone with a different experience than I, can contribute another opinion.


Old 05-20-2008, 10:13 PM
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Default RE: 1985 XJ6 3.4 Series 3 Starting / choke problem

Greetings Clive,

That sounds like a vacuum leak to me, perhaps intake manifold gasket? You won't likely get too much help from U.S. posters, I don't think we've seen S.U. carbs since 1974 MGB...and those were manual choke.
Old 02-24-2010, 10:59 AM
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Agree about the leak possibilities. I assume you have balanced the two carbs using the "hiss" test ?

Don't forget to check the vacuum pipe for the brake servo. This couples up to the inlet manifold somewhere. Even the brake servo could have a leak - does it work OK ?
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