www.jec.org.uk

I am a new member to the club from Victoria British Columbia Canada. I have a beautiful 94 MY XJ6 (SAJHN1748RC694856) with about 60k km. Recently, I have noticed that after decellerating at highway speed especially if the time frame is for several seconds, upon accelerating, the throttle pedal will not move with the normal amount of pressure. With increased pressure, the pedal brakes away and I am able to continue driving. I believe that the throttle body is gummed up with crankcase venting by-products and with the throttle plate closed and the intake vacuum exerting additional force on the plate, it sticks to the throttle body. Otherwise, I do not notice any other performance issues.
My query is on the preferable way of cleaning the throttle body myself. I understand that there are products that can be sprayed into the throttle body while the engine is running at off idle speed (AJ26 throttle bodies sticking). I prefer not to use this method. I am leaning towards cleaning the TB either in situ or on the bench with said throttle body cleaner. I also believe that the TB interior is fragile and I am concerned about affecting the throttle position potentiometer adjustment.
I look forward to your opinions. Bob in Victoria

Throttle bodies can gum up solid with crankcase breather oil residue.

Most have a very delicate coating around the throttle plate venturi area. Use spray carb cleaner, lint free rag and an old tooth brush to remove the sticky mess. Wear rubber gloves as the oil resdue is high in carbon solids and is difficult to remove from bare hands.

Also make sure that you remove all of the encrusted mess from the betterfly throttle plate and ensure that the plate moves without resistance after the cleanup.

The idle speed and evenness of the engine should improve after this maintenance.

Add to your maintenance schedual every 10k miles.

Also check breather pipes for cleanliness. Particuarly around the pipe fittings and connectors. Some parts may require pricking out with an appropriate tool to relieve any blockages.

For some reason, this maintenance is frequently overlooked at service time. It is just as important as spark plug changing to ensure nice even running.

Mike Kennedy. S-type Co-ordinator.

Mike has a good point, one other thing to check on XJ40 is the bonnet liner, this collapses with old age (just like me) and sags (again just like me!!), it then interferes with the throttle capstan movement, check the liner for damage, remove and renew as needed

Bob, did you solve your issues??