My '04 VDP has a slight buck when it is cold and I drive it on the HWY. The car feels like the idle is constantly going up and down like it can't settle at smooth speed. At first I thought it might be tire/road noise, but it is not. It takes some time for it to smooth out. It is quite pronounced and I am worried.

What do you think it could be? I would like to have a grasp on the problem before I go to the dealer or independent Jag repair shop. The car has 52K miles.

 

There is a TSB from Jaguar for rough running on cold starts, it requires an ECU reflash to correct a software problem. I just had it done, it helps but it's not perfect.

 

The service history on my car is very good. There hasn't been any major issues ever with the car, so perhaps this TSB was never applied?

How much does it cost to flash the ECU? Can independent Jag repair places do it?

 

Just call the respective shop and ask what they charge and if they can do it. Reflashing the ECU normally required the Jag PDU which is dealer-only. Mine was done under warranty.

 

Do you by any chance have one of the first of the '04s (VIN lower than G12000?). I believe this problem was much more prevalent on the earliest of the XJs. I do also, and have/had the same problem you describe. I had the powertrain control reflash done (actually a reflash of the engine computer AND the transmission computer), which improved the problem somewhat, but I still have some "bucking" when cold. I "sort of" recall having read somewhere that the only way to cure the problem completely is to replace the torque converter, which is OK if you're under warranty but I'm sure WAY $$$$ if you're not. My car is out of warranty, so I just live with it (only lasts for ~5 minutes and only noticeable at constant speeds when warming up).

 

I'll look at the VIN when I get home. I do have an extended warranty, but would like to know that it's covered before going down that road. Will update when I get a chance to look at the car. I do not drive it every day.