Finally, it's back together. I started it up yesterday and it ran great, check for coolant leaks and there was 1 that I have since fixed. I go to start it up today and I have a rough idle and cylinder 6 is misfiring. Also said misfire rate exceeds emission. Some background info. Both heads rebuilt. Timing chain both primary and secondary replaced. New spark plugs. Battery fully charged. I'm stumped on this one. Could it be a fuel problem?

 

 

Try swapping that coil with another and see if the code moves with the coil or stays with the cylinder.

 

It stays with the cylinder. Would switching the wiring with the 1 next to it tell me anything or could that ruin the engine by changing the firing order?

 

That's a stupid question, idk why I just asked that.

 

I switched some coils around yesterday on the drivers side only, which is where cylinder 6 is located. Cylinder 6 is no longer misfiring, but cylinder 7 is. Which is on the passenger side. I didn't switch any coils between the sides so how could this happen?

 

Page 16 has the answer.

bob

 

But the question is why it's misfiring.

 

If the misfire is moving when changing the coils, then it's likely having a faulty coil.

What Bob wants to point out is that you should double check your cylinder numbering. Your OBD interpretion of p0306 is following the ISO standard for cylinder numbering. But Jaguar didn't use the ISO standard for their cylinder numbering (at least not back then for the AJ26/27 engine layouts).

Here's what I'd suggest to be double check:
- get the proper DTC catalogue for your car and model year (e.g. from jagrepair.com)
- read the codes and ignore your reader's description behind p030X
- look up the meaning of the code in the before mentioned DTC catalogue and use the cylinder layout Bob has provided to identify the right cylinder

Cheers, Alexander

 

I looked it up, it is cylinder b3(7). It says possibly causes are from code p0300 but I didn't have that. It means random misfire. I'd like to add that it started fine after I had everything together. I put water in the coolant system to flush out any contaminates and to find any leaks. There was a leak right up by the throttle body and water sprayed all over eventually. I didn't think anything of it and that's when I started it the next morning and found these codes.

 

From that description it's water ingress on the engine loom - no major issue, just blast WD40 or similar into the connections on the engine harness within reach of the coolant spill.

 

When you say engine harness do you mean the wires that go to the ignition coil? I'm not sure I fully understand.

 

Yes, the coil harness. The coil covers have a thin gasket that leaks with age. I would remove all the coils from that side, but leave them connected to the harness. Then get any water out of the plug wells and coil boots before re assembly.

A little grease on the cover gaskets will help in keeping moisture away from the coils and plugs.

 

There is no water in the coil that Is misfiring.

 

It's possible that it evaporated since then (because of warm engine) leaving corrosion behind causing intermittent failures. So do yourself a favor and check all coils, coil boots (in particular the contact springs inside) and spark plug terminals for corrosion, clean the contacts, treat them with contact grease/spray and you're safe. If you want to do it thouroughly, get the spark plugs out and check the threads and the collar+washer for any signs of extended corrosion/contamination. As the metal case/shell acts as a ground for the spark plug, major contamination (esp. at the collar and the washer) will result in a poor ground connection.

 

Ok I will clean the coils well. But as I stated above I did rebuilt the heads and the spark plugs are new.

 

I did read that, but my statement aimed at any coolant residue/other contamination which might have been build up between the spark plugs and the head. Maybe there's some contamination left from before the head rebuild? Or had been the whole head sandblasted/thoroughly cleaned incl. the spark plug wells? ;-)

 

Yes when I had them rebuilt they were sandblasted and looked new afterwards.

 

Based on that it's quite unlikely...but for peace of mind no big deal to check the plugs, coils and wells...

So I was re-reading the story above and you posted that you initially got a misfire on cylinder 6, means Code P0306, right?
The Jaguar documentation says for p0306 it's cylinder 6 = B2 = 2B. 2B is located on bank B = the drivers side (LHD).
A few posts later, you state that you now have a misfire on cylinder 7 = B3 = 3B. Which code do you obtain? P0307?
If yes, you might be on the wrong track, since cylinder B3=7 and cylinder B2=6 are on the same side!!!! It's not the passenger side! That's what Bob and I pointed out a few posts earlier. Check the attachment for clarification concerning the "historical" cylinder numbering for the V8 Jags before MY 2004.

 

I think you might be right and I was looking at the numbers for newer engine cylinders. I will switch b2 and b3 around today, and let you know what happens. Thank you for that, actually gives me some hope.