Hey Folks -- I'm a relatively new owner still trying to learn my way around the car and not particularly savvy when it comes to doing my own repairs.

My 1996 XJS starts just fine and idles ok. Once I hit the accelerator, the engine revs up but does not return to normal idle speed. I found the accelerator cable and, by turning the do-dad (the thing that the accelerator cable connects to), can manually return the engine to idle speed. I tried dousing the do-dad with spray lubricant (LPS2) but there wasn't any significant improvement.

- start the engine
> idles appears normal
- engage Drive and accelerate
> engine speed increases normally
- remove foot from the accelerator pedal
> engine speed does not return to normal idle speed

Does anyone have any suggestions? Thanks.

 

I will assume the 6cyl engine, not the V12, you did not say.

NOT wishing to mess you around, but have a peek in the X300 Tech Section. There is a longish, current thread on just this issue.

The 6cyl engines do suffer from the return spring, inside that do-dad thingy, binding. Jagaur issued a TSB (Technical Service Bulletin) about a fix.

The AJ16 6cyl engine and system, in the XJS and the X300 are the same.

Good luck

 

Most likely, the throttle body needs to be cleaned. It gets gunked up over time.

It's certainly something you can do yourself. I would recommend removing the throttle body to do a thorough cleaning. Be careful not to let the carb cleaner fluid collect at the bottom, which can happen if you choose to do the cleaning in place. It can ruin an expensive throttle potentiometer sensor.