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#1 rich idle

Posted: Thu Jan 15, 2026 10:59 am
by MarkRado
Following a thorough engine and carb rebuild (removing all emission equipment) and sorting out problems (due to defective new parts) the engine is running nicely now with the help of a friend with oscilloscope and gas tester.
We see (a low) 2% CO above 1500 rpm but it is still very rich at idle (7% CO, acrid) with no significant reaction to adjustment of needles.
I checked orientation of choke discs and mounted a transparent hose between the carbs to see if fuel from the choke is shut off (which it is).
I am stuck at the moment and kindly ask for your ideas,
thank you

Mark

#2 Re: rich idle

Posted: Thu Jan 15, 2026 4:51 pm
by Gfhug
Mark, you’ve posted in Series 3 yet your profile suggests you have a 1963 S1 OTS
Some forum members don’t always look at sections outside their area of interest and/or knowledge.
Maybe move to S1 or technical?

Geoff

#3 Re: rich idle

Posted: Fri Jan 16, 2026 2:42 pm
by MarkRado
Hi Geoff,

thank you for your remark.
I should have made clear that I am working on a standard E V12 with Strombergs.

Mark

#4 Re: rich idle

Posted: Sun Jan 18, 2026 6:54 am
by lowact
Didn't Jaguar add all that so-called “emission equipment” precisely to resolve the issues that you now have, high idle CO …
What do you mean by “choke disc” and “fuel from the choke”? What temperature compensating valves do you have, the ones with or without the vacuum hose connections?