I have a '98 XJR with 92,000 miles. Sometimes when I start the car, it has a very weak idle, and I am able to change the position of the shifter, but the car does not go in to gear (the car will just roll). Turning off and restarting the car always solves this problem.

Any ideas?

Thanks!

 

Have you let it idle long enough to see if a restricted performance light comes on? I think it takes about 2 minutes at idle. If you have a code, that will help diagnose.

 

Inconsistant idle quality on cold start can sometimes be caused by low fuel pressure on XJ8. This is the first symptom of intermittant connection to , or operation of, the fuel pump. You will not get a DTC if this fault is present.Have someone test the fuel pressure before a cold start to see if this suggestion might be relevant. There are many other possible causes but this is one I have seen and is easily confirmed or denied.

 

I love my fuel pressure gauge.

 

change the position of the shifter??

 

Sounds like dual linear switch fault? Bring shifter out of park, but wont engage gears. Cycle ignition and is fine.
Weak idle though is probably unrelated. Fuel pressure problem is likely. But could be vacuum leaks...clogged breather. Anything really without more info.