Hey folks. Did something lame yesterday. Checked the oil in my 2005 XJ8L before running into town. It was a little low so added 1/2 quart. Being in a hurry, I left the fill cap laying on the engine and drove off. 8 miles later I get the Restricted Performance light and blew a little white smoke. Pulled over when I realized what I had done. One day later and the car will intermittently blow white smoke and get the Performance alarm. When I replaced the cap no oil had blown under hood and oil level is good. What's going on.

 

More than likely there is oil in the intake from the PCV system when you were driving without the cap. It may take a few WOT before you start to draw all of it out. I would check the fuel trims, and if it were mine, do a battery disconnect and do a relearn.

 

That makes sense. The puff of smoke only happened once during my approx 16 mile round trip to town this morning. The engine is purring as usual. Excuse my ignorance re the battery disconnect and relearn. Please explain.

 

When you disconnect the battery, it clears the short term fuel trims. Both emissions and fuel trim will go through a relearn process. There is a process you follow once the battery has been disconnected to prepare the vehicle.

CAUTION: Before disconnecting the battery, ensure the ignition is turned off for at least 15 seconds. The battery should never be disconnected with the ignition switched on since this will not allow modules to shut down correctly and will result in fault codes being stored and spurious faults being induced.

Ensure a minimum interval of 20 seconds from battery disconnection to battery reconnection. When reconnecting a battery cable, ensure that the operation is carried out in one clean connection to avoid unwanted electrical ‘spikes’ in the system.

After battery reconnection, the engine management system must ‘re-learn’ the limits of throttle pedal travel. This is to ensure correct adaptive settings are stored for kickdown operation. Re-programming is done with the ignition switch in position II as follows:

Slowly press the accelerator pedal fully through the kickdown detent to the floor. Release the pedal and repeat the action.

You will then need to reset the radio, windows and other items from the Pre-Delivery Inspection section of the Workshop manual.