Hi. I'm.having trouble with the central pedestal that controls the opening of the throttles on my 1977 pre HE XJ12. It is not fully returning to the stops under the force of the return spring, causing a very high idle.
I want to disassemble and clean it and replace the return spring, but my Haynes manual doesn't cover this. My question is- should I be aware of anything when taking it apart and reassembling?

 

Yep.

Remove the TPS (Throttle Position Switch on yours) prior to removing the 2 hex screws and pulling the plate/shaft out.

Generally, when that plate is out of the way, a few drops of ATF on the innards, leave it soak for a beer or 3, and all is usually OK.

I have never replaced that spring, they seem robust, just some lube every few years or so, and they be happy.

 

I like the use of beer as a unit of time.

 

HA,

Is there a better way???

Wife sees you sipping, and asks the obvious.
Reply :"just waiting and need to pay attention", job done.