Hello, new member here!

After searching for over a year, I finally found the XJ6 that I was after. A one owner, 1996 Carnival Red VP! The car was traded in at a local dealership with only 35000 miles on it. Overall, the car is in fantastic condition. Spent it's entire life in California up until a few months ago when the owners moved here to Washington.

The issue that I'm having, and it doesn't happen all the time, (I would estimate about 50% of the time) upon starting, it seems to idle roughly. It stops within 10-15 minutes of driving, however. Other times, it idles smoothly upon startup. Would anyone have any suggestions as what it could be?

Check the archives for spark plug recommendations. These cars are sensitive to brand and spec and yours are probably ready for the first replacement set!

Your EGR might be sooted- removal and cleaning is an easy DIY. All sorts of stumbles are reported to be improved by cleaning the TB, but I had no such problem in my many thousands of milkes driving my X-300.

I assume you have no check engine light. In spite of that, you may be getting a dodgy oxygen sensor. It can be tracked down using diagnostic charts from the OBD interface.

After that, any number of control elements can cause drivability issues- temperature sensors, MAF, ignition coils and on and on. Many times it is just a process of working through the most likely to the less likely. Having diagnostic software to observe the various signals makes it more scientific in the guessing process, which can save lots of money that can be spent changing parts that are good!
Welcome and GOOD LUCK!

did you get the idle all sorted? if not shoot me a message and i will give you plenty of tips to use.... i did this on my 1997 4.0 XJ6 vp..... cheers