I have a 2013 jaguar XF3.0 all-wheel-drive supercharged. Recently it has started doing high revs. The only times it does it is after it is warmed up when restarting it. It varies each time. It will idle down after about 10 to 15 seconds. When I first bought the car about a year ago the engine light came on and I did a code read and it was for the mass airflow sensors. I cleaned them and it came back on so I replaced both of them. But it just recently started doing this rev upon warm motor start up. Any ideas would be great thank you.

 

I had that problem with a 2014 RRS 3.0. It was a vacuum leak caused by the acoustic symposer (or whatever they called it). It would rev very high for about a minute and then settle down and drive normal. But it did give misfire codes as well. I disabled that silly symposer by fabricating a block off plate and the codes and idle issues went away immediately. If you don't have that system, it could be an air leak somewhere else along the intake. I have an automotive smoke machine that I used to find the problem. I read the same problem can also be cause by a torn EGR diaphragm, or a crack in the plastic valve covers.

 

Thank you i will look into that.

 

Had the same issue on my 2014 3.0 SC AWD, have you looked at this post below, I did a bit of a tutorial as to how I fixed my issue.

high revs/ lean bank 1&2 - Jaguar Forums - Jaguar Enthusiasts Forum

 

Replacement was pretty easy. Old one was ripped badly. Still have high revs on start up.

 

Good thing you replaced it. Next, it’s time to break out the smoke machine.

 

Wow, That's a nasty rip. I would agree, if there was nothing else obvious when disconnecting and then during re-assembly, I would be looking at another leak somewhere.

I honestly would have thought after finding the ripped PCV diaphragm, replacement would have solved to.