I have what I think is the same issue going on. I have swapped the coils and checked the battery and the battery seems good (is only 2 years old and on charger at all times when not driven) and the coil swap did nothing. In my 2000 XKR there is no ignition module and ASI doesn't rebuild the PCM (at least their website doesn't indicate that it does so I would be curious to the solution whatever it ends up being.

 

I went to a Jaguar event last weekend and there was a specialist independent jaguar garage there being represented. After a chat with the owner I booked the car in for next week. He seems to think it's not an ecu problem but a bad earth somewhere. Jaguar main dealers take their cars to him when they cannot work out what is wrong which sounds encouraging. I will post my results as soon as I find out.

 

I will be curious to hear what he finds and if it is a ground where it is located (although I suppose it could be one of many potential grounds).

 

~I finally got my jaguar back from the specialist and the car is working fine. The main diagnosis was one of the new coil packs I fitted was faulty and was replaced with a second hand tested one. Discussions with the mechanic revealed that my replacement coil packs were unbranded, and despite some good sounding warranties on them they do not last very long (I dont think mine ever worked!). I dont know this to be a fact, but it was his opinion. The original Denso ones are pricey and the mid range Lucas ones are the best ones to replace OEM parts with or a fully tested original second hand part. I had no feedback on any further testing of the earths in the ignition circuits as the replacement coil pack cured the fault.

Now this is where things get a bit grey. I had a spare ECU in the boot of the car and the mechanic fitted it to the car and programed the key to the security module just for completeness. Now the car works as well as it used too but suddenly all my remote controls for the car are suddenly working again. They stopped working 2 years ago, so i used to unlock the car and turn the key before the 30 seconds expired and the alarm went off. There is no chirp from the alarm as the doors are locked or unlocked and only the lights flash. I suspect the alarm is not working. No big deal there as the car is securely garaged and never left out overnight or for any time during the day.

My problem is thus; the faulty coil pack was a simple test and replace the coil pack. The replacement ECU cured a remote not working problem. I cannot be sure however, if replacing the ECU cured some other intermittent problems. The only way to find out is to put the old one back in and run the car for a while.

A lot of suggestions was to take the car to a main dealer. However the garage i found was a specialist Jaguar garage with experienced Jaguar mechanics. Main dealer prices are £160 per hour and these guys are £60 per hour for the same, if not better diagnostic equipment than a main dealer. They are Hollygrove Motors, St Ives, near Ringwood in Hampshire.

 

Did you swap coils before taking it to the specialist and if so did you see the problem follow. I finally fetched my car from its storage location and it started out with restricted performance but by the time I got it home it had dropped off. Still have the MIL lit and haven't had time to take it out since it has been doing nothing but rain (starting to think I live in the UK). Interesting on the ECU, are you sure that the ECU didn't solve your restricted performance problem and not the coil?

 

3 of the coils were replaced before taking the car to the specialist. I replaced them because of the 3 codes the car threw specific to particular cylinders. Because the fault is intermittent like yours I am convinced that replacing the ecu is key to the successful resolution to the problem and not just a faulty coil pack deciding when it wants to work. I have no evidence of this however but just a gut feel. I think England is becoming a desert! I cannot remember the last time it rained. all the grass is yellow everywhere

 

Your gut feeling may be correct. I have read a few posts about ECU problems on the early model years. I couldn't seem to find a good one, but here is a related one -
https://www.jaguarforums.com/forum/x...-please-97673/