Hello! I'm new here and hope I am posting this in the right spot. I recently purchased a 1988 xjs convertible, which needs a bit of work. It's not in overall terrible shape, but was left neglected. I'm trying to figure out the throttle return situation. Mine currently does not on it's own. Surely there is a spring, but I am not seeing one in the diagrams that I've found. Can someone lead me in the correct direction? I would like to get this addressed so I can fix the surging problem. I was also looking for a good source for proper replacement parts overall. Its said that the cooling system should be checked, so I am going to go through that as well.

Anyway, thank you for any help!

 

There is a spring inside the alloy wheel that the throttle cable winds around. Not known to cause many issues.

BUT

The shaft of that capstan, held in place by the 2 small hex had screws on top, is known to bind in its bushes due to lack of lubrication.

DO NOT simply undo those screws and pull up. Removal is more involved, as there is the TPS (Throttle Position Sensor) at the other end of that shaft.

Unhook the throttle cable, and ensure the capstan rotates 90deg SMOOTHLY. It is does, move on. The cable may be binding? If that capstan is stiff and sticky, then surgery is needed, and will be explained later IF needed.

There are also 2 throttle springs on each throttle body. Make sure they are in place and GENUINE springs only here please. Generic can cause a full throttle jam, sounds like fun, it is not.

Also, the AAV, located on the rear of the B Bank cyl head, is KNOWN to jam, and cause surging and other havoc.

Some light reading attached.

OK, THAT 1ST ATTACHMENT ABOUT DESMOGGING IS A MISTAKE, AND I CANNOT REMOVE IT, IT SIMPLY WILL NOT STAY REMOVED, SO IGNORE IT, UNTIL I CAN SORT WHAT IS GOING ON, SORRY FOR THAT.

 

Grant, is it possible to lubricate this without disassembly? Like jamming the long plastic spray nozzel of a can in there?

 

Thank you so much! I will get on it this weekend and update on what I find.

 

Never tried, BUT, that top machined plate sits quite snuggly in its machined recess in the capstan. Might get a mist only that top are, and nothing down the shaft where its needed.