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Matt, Mechanical Engineer
Category: Jaguar
Satisfied Customers: 22756
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Jaguar xj6 twin carb with AED. Having just replaced inlet

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Jaguar xj6 twin carb with AED.
Having just replaced inlet manifold gasket car now runs at about 3000rpm when on choke cfould this be due to AED or other fault?

1st thing to check is if the carbs are pulled down evenly and have a good seal
and do the same for the inlet manifold joint

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.
Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.
Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

do you still need help with this?
Customer: replied 4 years ago.
Sorry for the delay, do you still believe this to be the case bearing in mind it only ran fast while on choke and went back to normal idle when the choke wenr off.
Hello Steve

thanks for the extra information

for it to idle fast then more air than normal must be finding its way in and as the choke will add extra fuel then this will raise the idle speed still higher so yes I do think that there's a vacuum / air leak still
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