Q: My 2004 Jaguar VDP Engine is misfiring/vibrating and its performance/acceleration is restricted!

asked by on December 25, 2016

In November 2016 my 2004 Jag Vanden Plas (8 cylinders) was vibrating at low RPM and the Engine Light in the Digital Information Center lit up and the following message appeared; "Restricted Performance" (very slow acceleration compared to when the car functions properly). I brought the car to a reliable mechanic near my home (not a Jag Dealer Mechanic). The Mechanic plugged his computer and read the codes and it said that Cylinder No 6 was misfiring and that the coil was most probably responsible. I decided to have all 8 Coils replaced since he informed me that when one goes bad, it is not long for others do the same. He also suggested to replace the Spark-plugs (with Iridium ones) and that was done. The car worked perfectly for 2 weeks until 2 days ago. Again the Engine Light was lit and the "Restricted Performance" message appeared. A new diagnostic by the same mechanic revealed that Cylinder No. 2 is now misfiring". Is there a problem with the Fuel Injection system? Thanks Jim

My car has 102000 miles.
My car has an automatic transmission.

Hello. The misfires, along with the symptoms you are experiencing can be caused by a wide variety of different things. The restricted performance light and settings are activated when the computer detects that there is an issue that could potentially cause harm to the vehicle’s engine and emission components. Power will be restricted in order to reduces stress on the engine and components. If you have already looked at the ignition system then a few other potential causes are fuel or engine management issues. If there is a problem with one or more of the vital components, such as the fuel pump, and injector, or a sensor, the vehicle’s air fuel ratio may be disturbed, causing a misfire. The same can also be caused by a vacuum leak, or another malfunction that allows unmetered air or fuel into the number two cylinder, or in more serious cases mechanical issues with the engine. A look at the fuel pressure and the injector for cylinder number two could help determine if the issue is related to the fuel system. As these sorts of issues can sometimes be difficult to diagnose, I would recommend having a professional technician, such as one from YourMechanic, visit your location to determine what may be causing your misfire.

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