Hi all,

I still have a handful of misfires on cylinder 8 and a couple on 6. They tend to happen more during morning cold start. They do not trigger a CEL. However my long term fuel trim on bank 2 is at -12.5 at idle and maybe gets to -7.5 under acceleration. Other bank is -3 LTFT at idle.

During my recent maintenance service I had all my spark plugs and fuel injectors replaced. There was some carbon on cylinder 8 spark plug. I also passed leak down test on relevant cylinders. I have not yet replaced coils, oxygen sensors or MAF sensors. I was thinking it can’t be the MAFs as I should have an issue on both banks, right? I could change O2 sensors as I’m due and replace coils on the misfiring cylinders, but would rather know the best way to diagnose the issue before buying parts.

Thanks in advance for your thoughts.

EDIT: This morning I had 2-5 misfires on cylinders 2, 6 and 8. Here is a snapshot of my fuel trims at idle.


Note short term trim is near zero (yay), but long term trim is -13.3 for bank 2. Bank 1 long term trim is also near zero. To me this suggests something is wrong with bank 2 fuel trim control. Perhaps this is causing the misfires. Is this enough info to replace bank 2 oxygen sensors?

 

Still have this issue, but now have new O2 sensors purchased and will install them soon.

However before I do that I was hoping to get feedback on the CATEMP11 reading above (>1600F). Is this number in line with everyone else’s? It seems very high to me, though I have no basis for comparison. My exhaust does make some cooling noises now when I park. That didn’t use to happen before. Any input here would be welcome. Thanks.

EDIT: It looks like this sensor is heated (similar to upstream sensor), so the number likely isn’t telling me anything about catalytic converter temps. I’ll update this post when my new upstream sensors are dropped in.

All the best.

 

Upstream sensors were replaced, bought the Denso ones from Rock Auto. They work fine, but did nothing to the long-term fuel trims. One of the old sensors was quite black (presumably bank 2 but tech didn’t take definitive note). Presumably due to running rich. Also swapped downstream sensors between bank 1 & 2, no change. Cleared adaptations no change.

So I think this is just how the car wants to run now. I have new spark plugs, new injectors, leak down test is fine, and new upstream O2 sensors. Not sure there is anything else left to do. Car seems to run well enough despite rich fuel trims, so I’ll shift focus to elsewhere on the car.

All the best.

 

Okay I'm now thinking of changing all the ignition coils on the driver's side to see if that helps. What is the best way to access them? There appears to be a black piece of foam material tangled up with some coolant lines in the way near the coolant expansion tank. I assume this needs to be moved out the way. Is there any trick to get that thing off without hurting all the hoses? Thanks.

 

Take a look at this thread. A lot of helpful tips

https://www.jaguarforums.com/forum/x...change-145292/

 

Thanks, I’ll check in on that thread for more details. I’ll update here with my progress on the fuel trim numbers.

All the best.

 

Thought I’d update this thread. I have been tackling this issue slowly.

Bank 2 coils and cat are now new. As my car is at 100k miles, I figured this was acceptable maintenance. Though the problem still persists. Fuel trims are slowly getting progressively worse on both banks. Bank 2 is now at -18 and bank 1 is -7 at idle. As both banks are now starting to stray from ideal trims, I’m starting to suspect something less bank 2 specific.

Bank 2 fuel line that stretches in front of the supercharger sounds quite noisy (clacking). Clacking sound gets largely silenced by gently wedging a flathead screwdriver between fuel line and engine, just behind the oil filter. Planning to run the fuel pump test with SDD soon. Thinking bank 2 might be more susceptible to pulsations in the fuel pressure as it is farther from the pumps. Though now even bank 1 is also starting to be impacted, potentially suggesting a pump is nearing its end. Hopefully the test will show one or both pumps need replacement and I’ll be done with this issue. Wish me luck!

As always, I’ll keep you all updated.

 

Very good troubleshooting! Hope you can get to the bottom of it.
Can you post your fuel pressure readings? At idle?

I watch these as I am still tuning the car and I know that if the HPFP pressure starts to fall off a lot of strange symptoms can show up.
Interesting that you hear a clacking too? Don't know if that means anything or not but I do know on my XJR it clatters a bunch at start up then really quiets down in a minute or two.
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Sorry for my slow reply, I was away on mini-vacation. My idle fuel pressure is ~1400psi in drive/reverse and ~900psi in park/neutral.

Im thinking the aging pumps are creating bigger pusaltions/ fluctuations in fuel pressure (peak to valley) as opposed to it grossly missing the desired pressures. There is a TSB for noisy high pressure fuel pumps (TSB says to identify which pump is problematic with SDD test and then replace noisy one) and I am wondering what generates this noise. My bank two fuel line is pretty noisy as it sounds like a cricket with a tiny jack hammer.

I read some other car enthusiast websites (different brand of cars) installing fuel line pulsation dampeners in their cars to smooth out pressure variances caused by injector timing/ fuel pump issues. Wondering if pulsations are related to my noises/symptoms.

Anyway I have a virtual appointment with a Jaguar master technician who will hopefully guide me in the right direction. I’ll let you know if I figure anything out.

All the best!

 

Okay so got some feedback.

The fuel pressure seems a bit high at idle (IIRC ~6200 kpas) he suggested it should be half the value. Also calculated load was ~50% (way off) whereas actual load was ~18% at idle (more expected).

Tested fuel trims/ loads with purge valve sealed off and they did not change, suggesting not fuel from alternative sources. This suggests fuel pressure is indeed incorrect.

Master tech suggested 3 possible scenarios. First, high pressure fuel sensor is off/ bad (can’t check, just replace). Second, fuel pump timing is bad (retime). Third, fuel pump is bad (replace, though this usually results in a lean condition, not rich).

Found out that the fuel system is convoluted. Two high pressure pumps drive pressure to the fuel rails, one pump for each rail (the rails do not physically connect at the junction to share pressure). However there is only one fuel pressure sensor on bank 1, so bank 2 is completely unmeasured. Therefore bank 2 pressure is assumed to be equal to bank 1 pressure. Therefore if there is any issue it is likely to be on bank 2 as it is not being modulated by actual fuel pressure readings. Crazy!

 

Nedoerr, looking at your last post and picking up on the tech's thought of pump timing. Could that have happened when you replaced your guides and tensioners?

 

Unsure about the pulse dampers?
Do the 5.0L SC engines have these? I know my old 2005 STR had 2 fuel rail pulse dampeners. They can fail and are not serviced separately. So the repair was to eliminate the dampers because when they fail they leak fuel.
Did not seem to cause any problems but that was on a non-DI engine so way different fuel pressures.
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Good thought, I had to go back and check my records. Turns out the issue preceded the timing chain/ tensioner updates, so apparently it’s unrelated. When the technician swapped the chains and tensioners he locked in ignition timing. My understanding is the fuel pumps are on a separate chain and that timing was not touched.

I just changed oil two days ago, so I won’t be performing the suggested steps for a few months when I need my next oil change. In the meantime I will read up on how the fuel pump timing, fuel pump replacement, and fuel pressure sensor replacement are performed. I won’t be doing the work myself, but I want to make sure I am doing the cheapest/ least invasive stuff first and not doubling up on labor costs.

I presume replacement of the fuel pressure sensor and checking pump timing (removing the vacuum pump to access?) would be best stuff to do first, then move onto fuel pump replacement if necessary.

I also want to understand the readout of the SDD fuel pump test. Is this a diagnostic test or is it just for determining which pump makes noise? I’ve only seen it recommended for a noisy pump.

Clubairth, you are probably right that DI systems with high pressure pumps don’t have/ require pulsation dampers; not sure. Now that my fuel pressure is measured as high, I think that is likely the reason for the fuel line noise. So I retract my earlier thinking that it was pulsations rather than fuel pressure issues.

Keep you updated as I continue to figure this out.

 

A short update.

I sent in my car to replace the guibo/flex disk and replace a faulty door lock. At the same time I had the SDD fuel pump diagnostics performed and apparently there was nothing definitive. The pumps tested fine and there was no significant difference in noise between the two pumps (according to the tech). I pick up the car tomorrow.

I am at a loss. I want to get the VAP tune on my car, but it seems foolish without getting this fuel trim issue fixed first.

I reached out to VAP to see if they had any ideas. Otherwise my next visit will be the Jag dealership. I just hope they don’t suggest re-diagnosing all the parts that have already been replaced...

Will update this thread whenever there is anything to update.

 

Long time no post. Thought I'd provide an update immediately before trying something I probably should have done a long time ago. With any luck this will be the penultimate post on this topic. Wish me luck!

A quick recap:
I have been working on this problem off and on for almost 3 years now. It has been getting progressively worse and no one knows what the problem is. The problem was initially noticed in late 2018 with a handful of misfires, mostly on cylinder 8. The misfires tended to hop around across the various cylinders of bank 2, getting worse or better with seemingly little pattern, yet leaving bank 1 largely alone. Bank 2 started running progressively rich and it got worse with time. Recently (again 3 years later) bank 1 has decided to join the game and is also starting to run rich with a very infrequent misfire. For the longest time there were no codes at all. No misfire codes, no rich condition codes, nada. I have changed almost every part that could be blamed and then some. Coils, injectors, spark plugs, o2 sesors, even a catalytic converter (bank 2 side). Note, the list of work performed has been abbreviated for readability. Anyway, no appreciable improvement.

Mechanics thoughts:
One set of mechanics thinks, based on boroscope images, that the underlying issue is a bank 2 mechanical problem (like faulty valve seals), requiring major engine work. A second set of mechanics (rather recently) noticed the car is over-fuellng at idle, drawing 10MPa at idle (should be closer to 4-5MPa). They think fuel timing is off, and that I should recheck fuel timing.

OBDII codes:
Well finally last month the stupid car finally started throwing some codes: first was a code for rich condition on bank 2 (apparently needs to be < -25% LTFT to trigger); a month later the bank 1 rich condition code came up; and finally last night code p0101 showed up suggesting MAF sensor circuit A has detected an issue. This final code is what I think points me in the direction of the problem.

Current hypothesis:
Code p0101 has visited a few members of this sub-forum, and often suggests the MAF sensor should be cleaned or replaced. Well like others on this forum I have already done the MAF sensor dance with no improvement, so that is unlikely the issue. A few years ago, however, Chris (aka Thermo) posted that cleaning the throttle body butterfly valve cleared his p0101 fault code. Furthermore that solution has worked for other members of the forum. So I think this could be my issue too. Im thinking that perhaps the butterfly valve is dirty, disrupting the airflow and blocking the valve from completely closing at idle. Perhaps this altered position is detected by the throttle position sensor, which is telling the car the throttle is partially open and thus requesting more fuel, which would result in the over-fueling being seen by one of the technicians.

So long story short, I will try cleaning the throttle body and hope this headache is behind me. I'll provide an update soon. Fingers crossed!

 

Old thread I know any update?

 

Sorry to bump this after so long, did you come to a resolution on this issue?

Thanks!

 

Hi all,

Sorry, been away for a while. Cleaning the throttle body helped a lot, the codes went away and the fuel trims went back to normal on bank 1 and to only -12% on bank 2. There are still some mild misfires at startup, so it’s still not perfect but vastly improved. I still drive the car daily and am enjoying it. At 110,000 miles now. Thanks for checking in.

All the best!

 

1

 

any updates? I have very similar issues!