a) X300 V12 P0307 and P1314; b) Knocking noise inside the car
 

I posted this thread in the wrong section first, so here it is again in the right section:

Hello everyone,
I've been having troubles with my 1996 DD6 (6.0 V12). It started to shake in idle (only very slightly though, but still noticeable in comparison to the way it should be) and consuming more fuel. I checked the fault codes and it showed P0307 (Misfire cylinder 7) and P1314 (Misfire - Catalyst Damage). Cylinder 7 is the frontmost cylinder on the left bank, right? I checked compression on that cylinder which is the same as on the other cylinders. Spark is also there and easily visible and audible. High tension wire has correct resistance. I think the misfires don't occur permanently, though as when I last drove it, I could suddenly feel a reduction of power which disappeared again. Is it recommended to change the coils and high tension wires and see if the problem disappears? Any other ideas? I also thought of replacing the fuel injector. Does anybody have experience with these aftermarket wires: Ignition Lead Set - LNA1509AA | Jaguar X300 - XJR | Jaguar | British Parts UK ?

My second problem is an irregular knocking noise, similar to an electric fuel pump. It occurs at idle and is only audible from inside the car. It doesn't come from the engine. As far as I can located it, it seems like it comes from behind the dashboard or the front floor. Is it a known problem?

Thanks for your help,
Valentin

Valentin,

a) You are correct in checking the frontmost cylinder on the left bank. Commonly known (among uncommon V12s) as cylinder 1B. A bank is right side, B bank is left side.

If the spark seems good, then go to the fuel injector. Check the continuity of the wires as best you can. They endure serious heat. Finding no anomalies so far, I would suspect the fuel injector. Good news is if the injector isn't injecting, you will have a misfire, but won't have any catalyst damage from unburnt fuel!

I wouldn't recommend replacement of ignition components just yet, since there is no proof of a problem there. The V12 coil packs and ignition system in general seem to be quite dependable. Inspect and clean up the electrical connections at the packs and the ignition modules on the right fender (under the cover).

b) Half a world apart, same issue. I can hear an odd rattling from the cabin too! It is hard to describe and hard to locate. It is irregular and only heard at idle in park. I have yet to discover what it is. My only thought so far is that the A/C condenser bushings are gone, and maybe it rattles at that engine speed. Still, it doesn't sound like metal to metal. We will keep working on it.

By the way, your english writing is very good. Is it your first language?

Thank you very much for your help, Richard. I will do as advised and let you know if it worked out.

Regarding the knocking noise: My Jaguar dealer told me that I should replace the fuel feed hose pulse damper NNA6053CE because it probably got stiff and causes the knocking noise. I ordered it and we will see if it solves the problem.

Thanks for your compliment on my English. My first language is German but I need to use my English frequently for business transactions which might have improved it.

-Valentin

I had the time for further checks today. The injector on cylinder 7 is pulsing; disconnecting it causes rougher idle - meaning cylinder 7 is currently working. I attached two diagrams from my obd-reader, idle rpm and O2 Sensor. Both O2 Sensors have similar curves. Any ideas why the engine could run so unsteady?
Thanks,
Valentin

https://cimg7.ibsrv.net/gimg/www.jag...b708e6dc23.jpg

https://cimg8.ibsrv.net/gimg/www.jag...48492c40ea.jpg

Just a guess, but perhaps this injector is partially clogged and sprays less fuel than the other ones do?

Valentin,

Any progress with the rough idle or the knocking noise yet? I agree that the fuel hose pulse damper could be the cause of the knocking. Perhaps by changing that hose your idle smooths out? Wouldn't that be nice!

I still have that knocking sound. It is disturbing the otherwise quiet cabin! I have noticed that the fuel line (that feeds at the A bank) has a strong pulsing vibration where it crosses over from the left, at the front of the engine. It is a much stronger pulsation than the return line. So Valentin, if you're around, did you replace that fuel line/pulse damper with successful results? Anyone else noticed this rattling?

My car has suddenly developed these exact same symptoms with exact same P codes. Did you guys ever get to the bottom of this?

Hi John,

He didn't report any results and hasn't been on the forums since 2015. So back to the basics of verifying electrical connectivity. There is a slight chance that the spark plug at 1B could be older than the others. Position 1B is the tough one to reach and I remember reading that sometimes it is passed over at plugs changing time. First time I went for the plugs I broke the insulator at 1B because of the odd angle. So without knowledge of past replacement that's one check that must be made.

He also supposedly replaced the fuel line with the pulse damper. I could not locate a new part and did not replace it. I eventually went through the brake lines in the engine compartment, looking for loose pipes and potential sources of rattle. I used some pieces of rubber to isolate some of the brake lines along the firewall and it definitely made a difference. Very little rattling heard at idle in Park or in gear, usually none heard at all since then.

Great thanks for the reply. I found the connector to the fuel injector to be a bit crusty. I sprayed it out with cleaner and bent the tabs a bit to get better contact and so far so good. Drove the car to work which is about a 30 min drive and no issues but I’m not entirely sure this was it just hoping so.

Speaking of the pulse damper, there are two right? I could feel the hose that goes to the A bank pulsing, but the b bank seemed fairly smooth. I don’t know if that is normal or not.
https://cimg4.ibsrv.net/gimg/www.jag...3b38cb491.jpeg