Dear Forum,
I have attached Bank 2 STFT and LTFT for my 2005 XJ8L 4.2 (with no service records and 158,000 kilometres clocked) and a DTC showing a pending P0405. I have repaired a broken pipe between the air scoop and the air box, replaced the filter and cleaned the MAF sensor. My car is already running better! Now I am trying to decide whether next to use my limited budget to attack my Throttle-Body (very slight 'tremble' at idle), coils/plugs or to go directly to my 02 sensors?
Please could someone take a look at these and tell me (if it is possible to tell) whether I am barking up the wrong tree or (if not) what investigation to attempt next?
Best regards,
Ray

 

Have you checked for misfires due to oil-fouling of the coil units? You could have intermittent misfires due to failing coils, thus the lean STFT.

The issue is with Bank2, so it may not be the throttle body or oxygen sensors.

After a cold soak, remove the Bank2 coil units and inspect for oil-fouling or other deterioration. If there is engine oil present, the cam cover gasket and oil boss seals must be replaced.

 

Hello NBCat. Thank you for your response. I definitely have had a couple of misfires in the exhaust over the past two months that I have owned the car and I just about know enough to say these are usually caused by unburnt fuel igniting in the exhaust and that would obviously point at coils and/or plugs?

However, I have been labouring under the illusion that Bank 1 & 2 refers to the left and right sides of the V8? This is obviously wrong? If so, what is Bank 1 and Bank two, please?

How do I cold soak the Bank 2 coils, please?

 

With codes for only one bank it's hard to see how it can be anything that's common to both (so it's not the TB).

P0302 etc suggest you have a clear fault that needs fixing before you hunt for something else.

 

Thanks for your patience with me JagV8. So please check that I have this right - The first place for me to look is Cylinder 2 on Bank 2 (Right side of engine first coil when viewed from in front, bonnet open)?

 

Yes. See how it looks, what's in the plug well, etc and if all looks OK, swap it for another and see if the fault moves.

 

JagV8, what will I be looking for in the plug well?
if I swap number 2 with number 1, will the pending code change with it - bearing in mind that at no time has my engine light been on since I bought the car and all of the codes [ I presume except this pending code] are out of date?
In other words, is a pending code different from a historical code and is it therefore more of a current problem?

Regards,

Ray

 

Below is the cylinder numbering protocol.

You are looking for engine oil in the spark plug wells that can short the coil unit for that cylinder.

 

Or water. Or dirt. Or metal shavings. Or...

 

Very detailed info here:

https://www.obd-codes.com/p0302

 

Let's see if I am learning anything from your patient efforts, or whether I am still a total numpty!
I have attached photos of current freeze frame and codes. I (believe) I fully understand why the historical P0302 leads me to cylinder 2.

However, I am still puzzled by code P0405 (the pending code) - Exhaust Gas Recirculation Sensor A circuit Low?
Isn't this referring to one of the downstream O2 Sensors? What does it mean? As a 'pending' code, is this code as important (if not more important) than the historical P0302? Don't these sensors greatly affect fuel trims?
While I await your kind responses, I will get on with looking into cylinder 2 today and post results later!
Regards,
Ray the former Rover

 

Okay, I swopped the coil for cylinder 2 with that of cylinder 1. Car started as usual. Very slight tremor still there at idle. revs-up fine. Plug wells look clean. No oil, water dirt etc. Attached photo shows only thing I could see that was not uniform - Slight breakage in some material on the rim of number 2 coil boot? Can't imagine it is relevant?
Do I now need to clear the codes in order to see if they change? My problem with this firstly, since P0302 is not a current code, surely it will just disappear and not reappear until the engine check light comes on and secondly, won't I also lose my long-term fuel trims?
Have I got this right, please?
Regards,
Ray

 

It's a guess.

If you clear or don't - either could be wrong.

If you moved a coil that was faulty you'd expect the fault to show up as a code you didn't have before.

Pending codes (other than P1000/P1111) usually vanish quite soon or change to actual codes.

 

Thank you JagV8. Therein lies my problem with understanding these codes. My pending code refers to (I think) a downstream O2 Sensor and has been there since I first attached the code reader. The P0302 code is an old code which may not even exist anymore; have I got this right?
On balance, I think I will clear the codes and see if firstly P0405 is still there as a pending code and secondly, if P0301 comes up as a pending or as a new code?
Before I do this, I am going to wait to see what you think!

I have swopped out the coil in cylinder 2 with that in cylinder 1 and cleared the codes and P0302 has not changed to P0301? My pending P0405 has now disappeared and been replaced with pending P0302 & P1316.

So (do I have this right?). P0302 - Given the coil swap, the problem is not the coil on cylinder 2. Perhaps it's the plug?

P1316 - code is misfire and excess emission. Oxygen sensor has failed as per the Status since DTC reset shown below. Is this a combination of a failing spark plug and a failing O2 sensor?

Once upon a previous life, you simply screwed a glass-topped spark plug into number 1 and turned a mixture screw until it burnt bright blue/white and you KNEW that your petrol/air mix was at it's best. You attached a strobe to your battery and adjusted your distributor until the BTDC marks lined up with the marker and you KNEW your engine was perfectly timed. I am very open to explanation, but how is all this crap better?
Best regards,
Ray

 

Exhaust Gas Reciculation is different from the o2 sensors

 

Hello Robman25, thank you for your reply.
Is removing and cleaning the EGR Valve easy to do? Would it do any good?

Regards,
Ray

 

If the EGR one has gone then ignore it unless it comes back or there's some other good reason.

Still with P0302 but only pending... see if it flags. (Don't clear codes or it can't.)

But it may mean there's a real fault. Could be wiring/connector even the spark plug. P1316 also pending ... hmm. Not had a flashing MIL? It would usually and would mean really bad misfires.

Has it had the right spark plugs fairly recently?

 

JagV8, Thank you. I am going to look at the spark plugs next. I have no idea even what plugs are fitted, let alone when or what gaps they may have! All my tools are still in Cyprus, so I am going to have to buy another decent socket set and plug socket etc.
Jaguar ownership is difficult here. There is only one main dealer and they are only interested in selling new cars. If you take an older Jaguar to them, they charge you the earth and then farm the work out to one of the myriad small mechanic firms (peopled mostly by Syrians with sketchy English) huddled on dusty, dirty industrial estates in Sharjah (the Emirate next door to Dubai), where they can just about afford to pay the rents that would be impossible for them to pay in Dubai. Getting parts means a weeks delay and shipping costs from the USA or the UK.
It's fun!
Regards,
Ray

 

I have never had to do any work with regards to the EGR on any of my Jags.
Hopefully someone on here can advise on that, I wouldn’t even know where to start looking. But with the warning Circuit low I would look to replace the relay if there is one?

 

Plugs may well be as my engine: NGK IFR5N10.

They come pre-gapped (if you check be VERY gentle with the sharp central electrode) and are pre-coated with anti-seize.

I found the old ones come out OK if the engine is still hot.

Rear ones are awkward access but OK with UJs etc.

Due at the earlier of 10 yrs / 100K miles.