I've started a new thread because it is a little long winded but hopefully this will help others including 95XJSteve.

I have owned a 1996 XJS with the AJ16 engine since 2016 and have become fairly familiar with the car during that time. After a few years of troublefree driving, the car would occasionally stall out when I came to a stop. It only happened when the engine was hot and it always started right back up. Eventually it got worse and would sometimes stall while driving and the transmission fault light would come on. The only way I could drive when this happened was to keep a little pressure on the gas petal when stopping and keep doing that until I got home. Sometimes it felt like it was running on 3 cylinders. The next time I would start it (cold engine), it would run fine until it warmed up.

I was convinced it had to be an electronic component that would fail when warm. I spent months trying to track it down all the while getting very leary of even driving the car. I checked all the usual suspects and nothing seemed to be wrong with any of them. I cleaned the MAF, intake throttle valve, and Rochester Valve, replaced the EGR valve and some temperature senders, replaced the CPS and checked the IATC, TPS and all of the wiring. Nothing seemed to help and if it did it was only incrementally.

One day I got a clue. The accelerator petal was hard to push as if a kink in the cable or a stuck throttle valve. I went to the throttle valve and found the throttle plate was completely closed. I removed the valve and found that the set screw was not even touching the throttle plate and that a previous owner had apparently used the throttle cable to set the idle. I believe that over the years the accelerator cable had stretched to the point that allowed the throttle plate to completely close thus blocking all intake air to the engine. I set the throttle plate to .002 inches and that completely cured my problem. All of the electronics were working as designed including the IATC which would allow the throttle plate to fully close when hot and the problem was purely mechanical. My car is a joy to drive once again.

 

Awesome! Glad you finally found it!