Hesitation over bumps and dips
 

My '04 XJ8 had a fuel pump installed a few weeks ago and I've noticed, since then, that when I go over bumpy roads or dips in the road, my car kind of hesitates, jerking a little, kind of like it is downshifting. But it definitely isn't downshifting. That's just to try to give a description of how it is riding. Its as if it loses power momentarily. The bumpier the road, the worse it rides and its pretty horrible. Any ideas? Do you think its related to the new fuel pump installation? Did something else go? I only have 23k miles. There are no error messages.

Sounds like your ASC may be kicking in...this will give you the sensation of no power for a second or two until the traction system stabilizes.

If so, does something need to be adjusted or fixed? The car barely accelerates on an uphill bumpy road. It wasn't always that way.

Well, something simple you could do is disconnect the battery for about 5 minutes and then reconnect. This will clear out information the computer stores concerning "driveability". This information will be recompiled as you drive and the computer will "re-learn" your driving style.

However, if you do disconnect the battery you will need to reset/ re-enter the radio/security codes, and radio stations, etc. You should have these code with your owners manual (s), or if you don't the dealer can look these up using your VIN number and print them out for you.

And, obviously, you can have the system diagnosed and any system codes read that may be present in the computer.

I have attached detailed instructions....