If I do not drive my 05 XJ8VP regularily, I get the "restricted performance" message. I get the code for the left driver's knock sensor (USA LHD). I think the sensor is indeed fine because the car hesitates badly when I accelerate with the RP message. If I keep driving it (and accelerating often), the hesitation clears completely and the RP message goes away. The car will then run perfectly until I let it sit up for another few weeks. I am thinking I have a fuel injector(s) that need replacing? I used a bottle of Techron cleaner, but still have the issue.

Any guidance much appreciated!

Richard

 

By chance does it happen after it rains? If so check out the water ingress TSB. Water can be sneaking into your ECM...

 

You really need to run and clear all codes first. So we know what's current and work on that first. You may have multiple problems.
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it might be hesitating because the timing is super retarded. you can just plug in a new knock sensor and put it against some ferrous material and see if the problems come back

 

Disconnect each knock sensor from the harness (disconnect battery first) and resistance test each sensor. Value you want to see is about 200 ohms +/- 5%

If your value(s) are not in spec then you need to replace the knock sensor meaning you have to remove the SC