I had a bad coil (confirmed by switching coil locations). Replaced it and was proceeding with the required driving cycles prior to getting a smog certification. Unfortunately another coil failed after about 80 miles (again confirmed failure by switching coil locations). Both coils that failed were originals (date code 1999). At this point I am at 4 original coils (1999), two I just replaced, and two that were replaced by PO in 2010. I am thinking it makes a lot of sense to go ahead and replace the other 4 original coils. Is that pretty standard practice for you folks with older XK8 and XKR, etc ?

 

Mine were original and 3 failed pretty much at the same time. I ended up replacing them all just so I wouldn't have to deal with it again (I hope).



Dave

 

what plug type and gaps are you running?

fyi, the bigger the gap, the harder the coil has to work.

 

NGK Iridium BKR5EIX-11 Gap = .043


I believe I read that Jaguar recommended opening the gap up even more to correct idle quality problems, but that is stock for these plugs.

 

If you have a code for 1 then replace it but when the next one fails replace them all. I replaced them all in my xk8 & Stype.

 

I think those original Denso coils have timers in them so they all fail about the same time.


Dave

 

when I replaced all of mine, I used the following at considerably lower cost to OE - 30k miles since I replaced and no issues

For 1997 2003 Jaguar Vanden Plas XJ8 XJR XK8 XKR V8 Ignition Coil New | eBay

 

Looks like a good deal if they work, but I don't think any AJ26 engines have 4 pin connectors so the ad is slightly misleading.

 

Just a follow up that since I posted, 2 more of the original coils failed. Especially frustrating since I am trying to complete the monitors for a smog cert and have to start over every time I reset. So ordered another two OEM (at $125 each) and now will have all new coils as I should have when I started down this road. I am learning.

 

You don't have to start over, do you? Why?

Just change coil and drive. MIL if on will shortly go off (3 warm ups).

 

Well, that makes sense, I have just been clearing codes. The Comprehensive, EVAP, and now the CAT Efficiency monitors are a challenge to get complete. In the past 25 years I have only had to deal with two DTC or incomplete monitors on any and all of the Chevrolet and BMW we have owned (both were EVAP codes cured by new purge valves). The number of DTC (P, U, and B codes) on the XK8 have been an education in troubleshooting !

 

Every code clear also clears all monitors. For a simple fix, just drive, don't clear, if you have trouble getting monitors to set.

Though... I'd be a little worried WHY they don't set quickly. (Do read codes PDF / workshop manual for info and clues.)

 

Yes, I have tried all the driving cycles I can find, not just those specific to the XK8. Frustrating thing is that prior to the most recent coil failure, the CAT Efficiency had run without problems. The most recent coil failure occurred about 5 miles from home and I drove slowly with restricted performance. Worrisome factor is that I saw a momentary "CATALYST overtemperature" message, so I hope I did not destroy the CATS. (I thought fuel was cut to the cylinder with the bad coil so not sure why that would happen anyway). The O2 sensors seem to be responding correctly and I replaced the primary widebands with new OEM O2 sensors but no change. As a side note, I think that California LEV (which my 2000 XK8 is) requires 90% efficiency to pass whereas non-LEV is 80%.

 

I'm fairly sure Jaguar correctly describe their own cars. Very nearly always.