This is an odd one. Out of nowhere my 2000 XK-8 has developed a miss in one cylinder and has decided not to tell my scanner where it is because of an apparent communication problem. The miss occurs when the engine is started cold and continues for about 5-8 minutes at which point it just goes away and the car runs normally. Next morning, same problem. Should I try a hard reset of the ECU or can someone suggest an alternative course of action as the next step.

Thanks,
Max

 

The hard reset costs nothing and if it’s going to help you will know in a few minutes.

best of luck,

Z

 

Thanks, going to give it a try.

 

8 minutes is a long time. unplug coils see how it drops


anyways fix the comms problem

 

Is there a reason you would not simply do the reset? Its easy, fast and the only reset required is the windows. Put them partially down before battery disconnect and leave the trunk open until your ready for reconnect
Both are nothing muffins. The first time I reset my 2001 xk8 was not for a reset but to facilitate dash light bulb change. I was shocked that its performance was instantly better and was an unexpected benefit. If that doesn't help be prepared in those minutes, to remove each spark plug wire 1 by one. If one cylinder is not firing youll notice no change and you can go from there. Bad wire, bad coil pack initially come to mind.

 

So long as you're not due a smog test you're probably OK to do a hard reset. It clears learned values such as fuel trims - but also the OBD monitors (used in many places for smog).

If a reset helps it's a (rather vague) clue to what might be wrong.

 

"when the engine is started cold" like January in Pennsylvania. Probably hasn't gotten a lot of driving lately. Cold temps depresses battery voltage and alternator boost volts once running. Check your battery voltage with some voltmeter and don't rely on the Jaguar gauge as it really doesn't tell the voltage. Report voltage back on this forum for further opinions.

Try putting a battery charger on overnight and try it the next day and see if it purrs like a kitty again. Head out to Autozone or equivalent and have them fetch the codes.

We have to assume the Check Engine Light is on if you have a miss. CEL on?

 

Wow, thanks for all of the great suggestions! I re-booted the ECU and nothing changed except that the CEL which went out when the car ran evenly stayed illuminated and it threw P307 and P316 codes indicating the problem was with cylinder #7. Subsequently found the coil pack on that cylinder was shot. Replaced it and the problem appears to be gone. I'm in the process of selling the car and wouldn't want to pass the problem along to the buyer. Again, thanks to everyone for their suggestions.