Lots of spark knock under gentle driving of my 2006 vanden plas. Car has less than 50,000 miles and still under Jaguar Select Warranty. Complained to dealership and no codes so nothing they can do but suggest I am not using good quality fuel. Problem remains regardless of where I buy fuel, premium only. Anybody here had similar problem and can make any suggestions of how to remedy?

thanks,
brdave

 

My 2004 VDP has started this same issue at 85000. I recently started purchasing gas at an out of town station on a regular basis due to my recent required travel. I also suspect fuel issues and have ALWAYS used premium fuel. Not sure how to trouble shoot.

 

On these and other modern cars, the ECU advances the ignition until knock is detected by the knock sensor. If you are using good quality fuel from a reputable station, it could be the knock sensor is duff. I am not sure what checks are made on this component; probably only for open circuit.

 

They could at least put a fuel pressure gauge on it.

They could look at fuel trims.

Why? Because sometimes pinging under load can be observed just before the fuel pump goes with no other symptoms. This is because the fuel pump cannot deliver sufficient fuel, the engine goes lean, it pings.

The LTFT can be a clue because the ECM will constantly try to compensate for an inadequate fuel supply be upping the trim.

 

In addition to what Plum has offered, I would look @ vacuum leaks as a culprit. Same idea as what Plum has offered with a slight twist, unmetered air leaning the mixture out.

 

Thank you so much for the suggestion. The car will be going to the dealership soon for repairs, will have them check it out.
Would changing the fuel filter be another step to determine insufficient fuel supply?

thanks again
brdave

 

Yes.
Put in a new one.
Cheap fix.
Rough on the system once it starts to clog...
Especially critical fuel pressures, etc.