i have a beautifull 1996 xjs v6 on the first start of the day the car will engage smoothly and just purrrr. However on subsequent starts it seems that the motor does not fully engage and idles very roughly and will stall out.(this does not happen all the time but is becoming more frequent) I can wait and try to restart the car but usually the rough idling will continue and i will have to wait at least a few hours for a clean start. I now have a service engine light showing as well as a transmission light which i think came on when i inadverntly put the car in 3rd gear while it was idling roughly. When i start the car i let the starter motor continue for a few seconds following the engine starting. If i just give it a quick flick and release the key it is more prone to the rough idling descrived above. has any one a cure for this rough idling? Thanks for all the help from this forum

 

Try cleaning the throttle body.