Hi all,

Been looking at 04-08 XJRs and found several good ones.

One in particular seemed pretty clean, but it was near impossible to accelerate from a complete stop smoothly - in fact, it was VERY jerky even if i barely touch the gas.

Perhaps I'm just used to all my MBs starting in 2nd gear, but this was sooo sensitive that I'm wondering if something's wrong.
Specifically, one indy mechanic thought perhaps the TCU wasn't updated and that's why it was driving jerky(since it's drive by wire so not manual cable)?

Can you XJR experienced owners please comment?
thx in advance.
Patrick

 

This can be many things, but a very common issue with what you are describing (Not just a Jag issue) is the throttle position sensor which tells the ECM driver input information i.e are you stopped and idling or full throttle etc...if this sensor has an open at any position it confuses the ECM and hence the jerky or sensative reaction you are feeling. The most accurate way to test is with a lab scope (you can use a high quality ohm meter also) to see the electrical pattern or sweep of this potentiometer. Often you can have driveability problems with no codes stored. I recommend scanning first to see if you have any stored codes, then proceed from there.