Hey, all. 2000 XJ8 4.0 The other day, driving to work, display centre showed ABS, ASC, and traction control unavailable. A few miles later, I got restricted performance and CEL. Shortly after, CEL started blinking. Before I went to pull the codes, the ASC, ABS, and trac disappeared, leaving only Restricted Performance and CEL. I pulled the codes and got:

P0307 - Misfire Cylinder 7
P1316 - Excess emissions (probably unused fuel from the misfire)
P0357 - Coil pack misfire cylinder 7

I cleared the codes and it drove fine for 30 miles, the CEL and RP came back. I haven't checked codes yet, but I will after work today. I suspect the codes will be the same three. I know this is possibly a faulty coil pack, but why would it trip the other modules? Some people have mentioned the throttle body being the issue. I will also swap coil packs to see if the misfire jumps cylinders. I'm also going to check for moisture, dirt, bad connections to the coil pack. Any other ideas? I will update as I proceed.

Cheers from Southern California.

 

It's a good point to start with checking the coil pack. Watch out: Cylinder 7 for the "old" Jaguars is Cylinder B3 = LHD drivers side, third cylinder from front.
http://www.jagrepair.com/images/Auto..._numbering.pdf
See the pdf in section "historical numbering".
The cylinder numbering of the old engines are not following the current ISO standard. Lots of people have been mislead by this fact.
As soon as you solved the coil pack issue, let's see if the other issues re-appear or not.

 

Great, that's the one I thought it was. I think owner's manual says something different. Weird. I'll report back my findings. Thanks, mate.

 

Seems pretty clear it is the coil pack on B3. Try switching coil packs with B4 and see if the code moves.

 

Will do as soon as I get home from work. I really hope that's all it is.

 

So, I pulled the codes again and got the same 3 as before. I tested battery and alternator and they both were normal. Next, I checked coil pack 7. There was some light dust, but not much, and no moisture. The pack seemed to come out too easy, as if it was not seated properly onto the spark plug. The plastic around the connector mouth seemed to have been cracked, with glue being used to repair it from the previous owner. Nothing was loose, but it didn't look right. I swapped pack from 7 with pack from 6 to see if the misfire jumps cylinders. When putting pack 6 into cyl. 7, it seated and had a suctiony snap onto the spark plug. The suspected faulty pack from 7 didn't do that, and seemed to just lightly touch the spark plug. Anyway, I cleared the codes and am waiting to see if the misfire comes back. Hopefully it will be in cyl. 6 now so I know for sure it's the coil pack. Thanks, guys.

Here is the (suspected) faulty coil pack with black metal, and the good coil pack to compare.

 

This "glue" has nothing to do with any subsequent repair. That's the way how the internal life of the coils is enveloped. That's no repair an experienced enthusiast can and would do.

Usually you're good if you get 1-2 used coil packs off eb** and put them on the shelf, as the original ones are quite costly. That's how I replaced already two faulty coils.

Best regards, Alexander

 

By the way - as an amateur mechanic you can usually not assess if a coil pack is on its way out - at least not from the outside.
So the best way is to move it around and see, if the code follows the suspect coil. Or replace it with a good one right away.

 

Good to know, thanks. I just thought it looked weird. The problem probably has more to do with it not seating onto the spark plug properly, but I'll see if the code moves with the coil pack.

 

That coil doesn't look OEM - a pattern part. As suggested ebay or this forum for cars being parted out would be the first place to snag a couple of second hand OE Denso spares. Like the spark plugs and O2 sensors - they wear out so having some on stock is a good thing

 

Yeah, that's a great idea, I'll be looking for some.

 

Okay, so the weirdness continues:

After I swapped coil packs (7 to 6), I was hoping for a misfire in cyl. 6, which would mean the misfire jumped with the coil pack. On my way home yesterday from work, I got misfires and restricted performance all the way home, but no CEL. Right as I was getting home, the misfires stopped, but the engine was still not running 100%. Seemed a little loss of power and a few hesitations. Tried to pull the codes, but nothing came up. Today on the way to work, the misfires and RP were on and off, but seemed to be worse than before, but still no CEL.

Also, that annoying drivers window glitch came back after only 2 days since I did the hard reset to fix it before. Am I looking at a larger electrical issue that would cause this as well as the misfires?

 

Well, then the misfires are not severe enough to set a code. At least you don't have any codes on cylinder 7 anymore...
My advice is still to get an used, but genuine Jaguar = Denso coil pack and replace it with the suspicious coil pack, which is apparently not OEM and on it's way out.
Cheers, Alexander

 

Yes, I think I'll do that so I can know for sure it's not the coil pack. Thanks, mate.

 

You're welcome! Fingers crossed!

 

I recall a member posting on the X300 forum a couple years ago that a misfire that was not severe enough to set a code caused a similar window issue. Once the misfire was corrected the window worked fine.

 

Okay, so then it seems it would be a larger electrical glitch that happens to affect the other modules. Someone on a facebook group suggested throttle body. Could this be a cause, or is it more likely something between the battery and the coil pack?

 

ONE MORE TIME!!!!!!!!

bob

 

Thanks, Bob, I haven't seen this, but I will check the solder and fix if necessary.

 

Sorry for not updating, had to wait to order the coil pack. Just arrived yesterday, and it seems to have fixed all problems. The engine is running SO smooth, there is a noticeable growl to it, it sounds and feels healthy, and I have way more power than even before the misfire, which leads me to believe that the coil was weak to begin with. Thanks, everyone!