hows the battery? Test it, if your battery is pooched you get all sorts of phantom codes, also do the swap coils test.

 

It is not uncommon to have more than one coil to fail and at times two. If your plugs are good and no oil in the plug cylinder you may have a bad coil. You could have a problem with the fuel presentation to the cylinder and that may be a matter of cleaning the TB, fuel injectors and or your fuel and air filter. A coil could be bad but I would not replace one until the other is checked.

I see that you have a suggestion to check the battery and that is never a bad idea.

 

swap the coils, and see if the fault codes will follow the coils.

 

I am seeing the same problem in my own 2005 2.5 l X-type.
Same codes - P0300, P0302, P0304, P0306, P1314, P1316 - which I have interpreted as 'Random misfire in cylinders 2, 4 & 6 leading to bad emissions in the exhaust which could damage the cat'. Would others agree with this ?
I have tried swapping coils for known good ones, and the spark plugs seem fine except for a little soot, which I put down to unburned fuel due to the misfire.
Following the procedure in the workshop manual, the power to pin 1 of the coil connectors is 11.8v (should be >10.5v) but the resistance between pin 3 and ground seems to vary intermittently between 3.2 ohms and open circuit.
As this is common to all 3 cylinders of one bank, I am suspecting a bad ground/earth/chassis connection. It seems to me that this is the next thing to look at, but comments are appreciated.
Would anyone here be able to help me by showing me where I will find the points where the pin 3 wires from the coils connect to chassis or engine block please ? Thanks in advance guys.

 

This is a link to the wiring diagram for your car.

Link http://jagrepair.com/images/Electric...al%20Guide.pdf

 

Thanks for that, Gus.
So, I've now got a good ground connection to the coils but still the misfire on one bank persists. I am rapidly running out of ideas on what to check next !
Please, guys, what might I have missed ?
I have ruled out the air intake system, as that is common to both banks of cylinders. All looks fine in that department anyway.
Since replacing the upstream HO2S, I am not getting any codes to indicate a faulty sensor. All I see is misfire codes and the bad emissions caused by the misfires.
Coils and plugs have been verified by substitution, and the wiring to the coils now checks out okay.
Can anybody please suggest what else I can test, examine or substitute as both the Jaguar workshop manual and myself seem to have hit a brick wall.
Thanks for your help guys.

 

A misfire could be caused by a few things your battery, plugs, coilpack, injectors and your ECM. You replaced the plugs and coilpacks and I would suggest pulling the injectors and have them cleaned. I will provide a link for that. If the injectors do not fix the problem I would have the ECM tested and I will provide a link for that. Often the battery is overlooked with the thought that if it starts the car it is OK. that is incorrect! Take the car to a shop and have them test the battery and the charging system to be sure.

Link https://www.injectorrx.com/

Link http://www.autoecu.com/index.php?p=1

 

Thanks again, Gus.
I hadn't previously considered the injectors because it would seem strange to me for all 3 on 1 bank to fail while all 3 on the other bank are fine. Plus, also, I had previously dumped a couple of cans of injector cleaner through the system 'just in case'. I will see about getting them checked, or perhaps swap for known good ones ?
I will also see about checking the battery, which is actually only about a year or so old. Yet again, I had not considered that as it is common to both banks of the engine but the fault codes show that the misfire is only on the 3 bank 2 cylinders, while bank 1 is not showing any fault codes.
Any other ideas ? Am I correct in ruling out things which are common to both banks of cylinders because the misfire is only on one bank ?
I'm getting desperate now as the car has been undriveable since New Year !

 

That does make a bad connection or the like more likely.

Usually the PCM fires a coil by switching to ground so the power wiring is perhaps most suspect.

 

Thanks JagV8 and yes, those were my thoughts initially too. Imagine my dismay when, following Jaguar's own test procedure, I found that the power supply to the coils was well within spec ( 11.8v against >10.5v) and the ground connection also (3.2 ohms against < 5.0 ohms). I haven't worried too much about the 'firing' wires as they are separate for each cylinder and there is a whole bank showing the same fault. The 'sense' connections, however - which I guess are there to verify that a coil fired - are one per each bank. However, I would not have thought that this could cause a misfire but perhaps report it instead.
So, for the moment, I remain as puzzled as ever !

 

Taking an alternative approach, I equipped myself with a can of carburettor cleaner and made sure that the mass air flow sensor and throttle body & butterfly valve were nice and clean. I'm sure it couldn't hurt but it didn't seem to make a difference.

In some photos I've seen, the wide corrugated hose which runs from air cleaner to the throttle body is held on at each end with hose clamps. Also, so is the ribbed breather hose which goes from the front cam cover to inlet manifold. On my car both of these hoses are simply pushed into place without any additional clamps or clips to hold them. I was wondering if those clamps were something non-standard which had been added to some cars 'just to make sure' as when I got mine there were none fitted.
The breather hose is quite a loose fit on the one-inch spigot fitted into the bank 2 side of the inlet manifold.
Can anybody say if the hose clips are standard fitting and if being without them makes any real difference, please ?

Thanks,

 

Yes, this clamps are a standard fitting but as I have never and would never remove them I cannot comment on efficacy without them,

 

Okay, thanks Sov211, I have sent for some nice shiny stainless steel hose clips for the two hoses I mentioned.

In my hurry to re-assemble things - for the 99th time - I forgot something which seems to have given us another clue towards the cause of this mysterious problem.
With the air intake components all back in place, I started the engine and - lo and behold - it seemed to run smoothly with no misfires !

I let the engine warm up then tried increasing the revs progressively. When it hit about 3000 rpm it started cutting out and wouldn't rev any faster. Perhaps this was 'limp home mode' due to some other fault ?
I stopped the engine and read off the couple of new fault codes, and realised that I hadn't re-attached the connector on the mass air flow sensor !

Plugging the connector into the MAF sensor returned the car to its previous behaviour of throwing up fault codes associated with misfires on bank 2 only.
I tried and re-tried a few times and the results are repeatable: with the MAF sensor unplugged the engine runs nicely up to 3000 rpm then 'hits a wall', but with the MAF sensor plugged in I get continual misfires on bank 2 only (original codes, like before).

So, two new questions have arisen:
Firstly, does this indicate that the MAF sensor is faulty or could it just be air leaks in the air hose from air cleaner to throttle body ?
Secondly, if this is a problem with the intake system then why is it only affecting one bank of cylinders and not the other ?

I don't know if I am actually making progress with this problem or just getting into a deeper hole with it !

Thanks for the help so far, guys. Any further thoughts are much appreciated.

 

This car has a rev limiter when not in gear around 2500 / 3000.

 

When did this problem originally come up? Did the codes just all start at one time or did you start with one code and they you started to get multiple ones? Was the care running perfectly fine one day and then all of a sudden the next day you have issues? Have you done any work on the car recently or replaced anything just before this?

 

+1 rev limit

to protect engine & trans

 

This problem showed up when I'd fixed the previous problem: a faulty upstream heated O2 sensor on the front bank of the engine. The same misfire codes had been showing, as well as one to show the HO2S was faulty, so I replaced the HO2S but still get the misfire codes.

The current situation is that the engine runs beautifuly with the MAF sensor disconnected but shows misfires one all 3 cylinders of bank 2 when it is connected !

I am assuming that this indicates that the MAF sensor is faulty ?

If so, then why is it only affecting one bank of cylinders ?

I'm puzzled !

 

Well, not necessarily. With no MAF it defaults and may be unable to flag the real codes plus may well run open loop.

Put a good MAF (maybe yours is) on, then watch fuel trims (LTFTs).