Need help. Well maintained 2009 XF Supercharger has a compression issue and local Jag dealership mechanics are stumped. "Restricted Performance" light came on and I limped to the dealership.
Was a hot day 95 degrees and driving in congested traffic. Stepped on the gas... no response... no downshift, no additional RPMs... same RPMs no matter what.
Dealership had it for three days... said it was the mass air flow sensor.... Replaced... $500.
All well next day until afternoon, hot again 94 degrees, same problem. Same idiot light.
Limped back in. Had it for five days... "cannot duplicate"... "need it for a few more days to drive in hot weather".
Still no resolution.
Diagnostics confirms time and again previous "Restricted Performance", but mechanics are stumped.
Anyone.... any tech calls on this? any advice?.... Been through replacing multiple parts process before... and before we really found the problem to actually solve.
Many thanks, Joe
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You may have more luck in the correct forum for your year/model.

 

sounds like insufficient intercooler cooling which can lead to engine knock under boost and damage hence the RP. Should look at the pump which may be failing and or airflow blockage in the SC radiator. Have seen mice and squirrels build nest and debris around the radiator or just crud. This is just thinking out loud and what I would look into myself. The pump is a bosch pump and readily avail as an upgrade unit also. Worth a charge for improvement in sc cooling anyway. Otherwise there "should be" codes for restricted performance as well as freeze frame data to see what the car saw for restricted performance. Another thing to look at would eb the engine fan. If not fully running at required speed and airflow it can cause a running hotter than normal in traffic as you describe. Ie the fan runs but is failing and running slower than it should. Although this usually causes a ac complaint rather than restricted performance. SINCE YOU SEEM TO HAVE MULTPLE THREADS ON THIS HERE YA GO AGAIN FROM YOUR OTHER THREAD

 

You didn't say what the specific codes were that triggered the RP. Suggest you buy a code reader ($130 at Harbor Freight) just so you can read the codes yourself before delivering the car to the shop. I keep mine in the car always since things happen frequently as the car is getting older. Also you can do better price wise with a good independent mechanic. I was just charged $256 to replace the Mass Air Flow sensor by my indie.