Since a COVID layover I am getting codes P0171 & P0174 (Too lean bank 1 & Too lean bank 2), I have attacked all the usual suspects but this has to be something common to both banks as the codes trigger simultaneously. The car is a 2008 SV8 (4.2 litre supercharged), currently on 136k miles.

All gaskets etc common to both banks have been replaced, mass flow sensors cleaned, both are in rude agreement flow wise, I'm starting to think that this may be fuel pump but the workshop manual isn't particularly helpful and quotes only one value, it offers no range or tolerance information.

The long term fuel trim at idle is insanely high - 19.53%, this drops to around 3% at high rpm, fuel pressure starts at 330kpa (circa 3.3 bar) but falls even lower at high RPM, I'm really starting to suspect that the fuel pump is banjaxed but it is an expensive item if it doesn't cure the problem. according to jaguar the pressure should be around 4.5 bar, lower at idle, which makes me think fuel pump. This is NOT the filter as the car doesn't have one. The lambda on both banks is pretty fixed at 1. I'll probably replace the fuel pressure sensor and see if anything much changes but I suspect the fuel pump is on the way out

Just sounding out the experiences of others with these fuel pumps before I blow yet more of my XJS budget on the daily.

 

I think you have a leaking P/B vacuum connection. I fought the same thing on my old 2005 STR which had the same 4.2L SC V-8.
Read my long thread with multiple solutions as it will be expensive at a dealer!!

Vacuum Leak
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Ya know I was in there and had a poke about, the english became very 'unusual' - how the blue **** is anyone supposed to do anything back there - there's no way I'm getting the PCV hose off - I tried !! (the PCV has been replaced) - it also looks like the tiny vacuum pipes - nylon things into rubber elbows have expanded but I cant find the damn parts listed anywhere and going to a dealer isn't my first choice simply because of the 'dealer tax' .... for £10 of materials you need to provide a £100 investment - I don't think so. I'll study some of the links in your post - 10 out of 10 for getting that elbow off you have either smaller hands or a lot more patience than I ....

The last time I did I managed to destroy both windscreen scuttles because they flat refused to come out of the groove at the bottom of the windscreen - the clip on the scuttles actually tore off !!

I've checked the fuel pressure again and again and it comes up fine, the car's never thrown a low fuel pressure code and if this was starvation it absolutely would - since the pressure sensor is post any kind of filter so if flow was restricted pressure wouldn't be maintainable.

 

I bought this car for the engine mainly, but the thing is vacuum leak city. Even a pinhole sized gap will affect how it runs and bottom line, a smoke test is the only way to find it since the damn PCV hisses by design, and the ECU instantly compensates for anything sprayed to get a reaction. Many more threads about these codes on the XJ and S-type forums where this engine was more prolific, but I don't think I ever came across one where the culprit was the fuel pump. My latest were the Duct Seals going to charge coolers, $50 a pop. Still doesn't run as smooth as it should, and probably never will. JLR considers anything within 10% trims to be within spec, and with their garbage spec rubber and plastic, here we are.

https://www.jaguarforums.com/forum/x...-output-222911
Same story, trying to diagnose fuel, ends up being a bunch of rubber and plastic after smoke test.

 

Read my links as the smoke test will miss these types of vacuum leaks.
The only way I can find them is to monitor the STFT and LTFT in real time while spraying carb cleaner at very specific spots on the intake system. There are multiple places and don't forget the plastic ducting itself has caused these errors too. Take the plastic intake tubing off and inspect it and flex it to check for cracks.

What software are you using to scan the car?

Yes that back elbow on the SC engine is a bitch to work on. Again the links I posted have several tips on how to attack it.
Did you slot the back mounting bolt bracket as Brutal has posted?

Let us know what you find too. It might be something different this time?
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I do have SDD 1.5.4 but it is a pain in the butt to use and I think it has locked itself now based on it has seen an incorrect date and decided it is out of date, I have a copy of 1.5.9 that is supposed to be OK and work but haven't installed it anywhere yet. I also have a genuine Mongoose cable to go with it - not a clone, but I absolutely will not pay the prices Jaguar are asking to go legit with SDD I just don't use it enough and got fed up of the hassle using SDD presented.

So currently I use an iCarSoft i930, it is a pain in the butt to get to the fuel trims (so many pages in). The short term fuel trim seems fine and does exactly what you'd expect, never above 6% and swings around exatly as you'd expect maintaining appropriate lambda and yet the long term fuel trims are pegged at 19.53%, if you rev the engine to 2000+ rpm the long terms drop to 3 or 4 but the second you let off the gas they jump straight back up, as for Jaguars '10% is acceptable on long term' - my fat behind it is. Fuel pressure reads 380kpa (unless you look at 'fuel pressure guage' which is down at 320 or so but I've no idea what the difference is - I think one is corrected for manifold depression or something - but Jaguars wonderfully clear information offers no clues). The downside of the icarsoft is that the cable simply isn't long enough to plug it into the car and use under the bonnet.

I've gone through everything air filter to throttle body with a magnifying class, I didn't want to tear into the back of the engine apart because if I do that I don't care if it is faulty or not it is getting replaced - except I can't identify half the darn parts I need - those little vacuum hoses are suspect, as is the entire PCV arrangement - pathetic O rings give me no confidence and I have replaced them - flimsy cheap plastic ***** - the PCV is brand new and genuine Jaguar also.

I believe things like leaving an oil filler cap loose or the dipstick not fully home can cause this too as can cam cover leaks, which I don't have because I don't have any oil leaks - yeh really I don't - I did have when I got it though.

This isn't O2 sensors because I've replaced all 4, I've also replaced one catalytic, have the other in the garage but a thread stripped in the manifold when I did the one on the car which was pain in the hole to sort so it put me off attempting the other.

I've already replaced a bunch of stuff - I am so tempted right now just to rip the entire induction system off the car - starting to get really brassed off with it as I want to spend time on the XJS not all my spare time on the XF

 

I've just replaced the PCV hose on my SV8 because it cracked and was both leaking air out and letting oil up the PCV hose to the throttle body (if we're talking about the same hose that snakes from the PCV under the S/C and tucks under the throttle body). I can tell you the that part and how to get to it if it is.

 

If you have the hose number it would be appreciated - although I couldn't get the SOB off the back connector, couldn't even see it on the throttle body let alone reach it (and I did have the windscreen scuttle off)

 

Its this part: https://www.brit-car.co.uk/product.p...___jaguar___xf

It is indeed a bugger to get off.

You need to remove the S/C, the windshield scuttle, and the cross beam. Unplug all the electrical connectors to the right of the throttle body and move aside the sensors etc. Then remove the throttle body and you should how have just enough space to get the hose off. I broke off the hose near the throttle body which allowed me to rotate it to a position where I could use long grips to squeeze the clip and pop it off.

It goes on much easier that it comes off, like 2 minutes to fit after 2 hours of faffing to get it off. Also an ideal time to clean your throttle body as it can gets quite gunky if the breather hose isn't working properly.

 

The thing I forgot to say was you should feed the hose under the intake manifold before connecting it because you need to gently bend and rotate it about to get it through the gap, otherwise you'll have to take that off too. I don't recall clearly, but I think I fed the throttle body end under it, but I'm not sure on that.

 

I half wish I hadn't put it back together but I had to in order to put the XJS in - taking those scuttles off again bothers me more than pulling the top off the induction system. I'd pull the lot off if I had half a clue how to refil the intercooler for the supercharger - that sure isn't obvious and I've never checked the water in it - didn't even realise it was a seperate system until this week. Was your hose no good or just the PCV. Mine has a new PCV already, the two charge cooler links and the large square gasket / rubber plate underneath (on top of the SC) also got replaced.

How on earth do you get that throttle body off - I know its 4 bolts essentially but can't even see them let alone undo them.

 

The hose had a crack in it that was letting out air, and the PCV seemed to be letting oil into the throttle body up the breather hose. I replaced them both.

The trick I found with the scuttles was to push down the pins into the clasp then remove the clasp and pin. When pulling off the scuttle do it from the middle and follow the windscreen edge, the clip seems to fall away from the edge of the plastic following the window and if you don't go along the same line the track breaks off.

I used a collection of universal joints and extension bars to reach the bolts. The ones at the back were fairly easy, the one on the front right was more difficult because of all the wires and hoses in the way, but in general as long as the scuttles and crossbeam are out of the way it comes off easily.

The coolant is filled from the main expansion tank, there's an interconnect between the two and a bleed screw behind the driver side headlight cluster from the intercooler rad (diagrams below)

 

Bit of a pig to bleed at a guess - definitely a vacuum job.

I appreciate the information, I shall remember you while I'm removing the flesh from my hands and scaring the cat (the furry one in this case because she hangs around and inspects what I do)

 

PPS - you cannot remove the clasp on mine - it is a metal strip bonded to the windscreen, I confirmed it with the Autoglass chap that replaced it last week - the new windscreen had the same part, it was also bonded.

 

You'll need some hose clamp pliers too, the throttle body has two coolant hoses connected to it that are an absolute pig to get to. I tried for hours to remove them with the tools that I had then went out and bought the hose clamp pliers and they came off in a few minutes, its nearly impossible without them.

 

So to remove the throttle body I'll be replacing coolant also when done ? - that's disappointing - never a simple job is there ....

I do have the special tools for the spring type clamps if those are what you mean including one that has a ratchet mechanism

 

That sounds like the tool.
I also used some small hose pinch tools on the hoses at the back of the engine to stop them emptying out all the coolant.

 

does anyone have a part number for the hose for the throttle body to the hat? have researched and cannot find the OEm part. have seen the threads on possible alternatives. I had the same issue and same exact numbers on LTFT. replaced the part as listed here, but found tear on part i am asking about, so it still has an issue. I also replaced those tiny hoses, they had disintegrated, they were a major research project to find and figure out what went where.

 

Do you have a diagram or picture of which hose you mean?

 

AJ811355