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Yes readings on Bank 1 and Bank 2 are essentially the same, unfortunately, so not an easy way to pinpoint something specific.
Not certain how accurate it is, but I have run the fuel pump diagnostic routine in SDD several times and it always passes. Fuel rail pressure has never seemed abnormal to me. Actually the numbers always seem fairly spot-on, hand in hand, which is why I reckon there aren't any DTCs. As you say, what's causing the erratic behaviour's the question and I reckon the shuddering and roughness is caused by occasional too low RPM at idle. Whenever I increase throttle input/RPM in park, the roughness/shuddering goes away. Also curious as to why idle is sometimes as high as 1100-1200 in park. I've yet to find a way to measure the MAF sensors independently. And they are the originals. I can get a pair of new genuine assemblies for under $200 but wouldn't be much help if that wasn't the problem.
Going along with RPM causing the shudder, usually increasing electrical loads, etc, like I've said before are additive and lower engine RPM causing ever increasing shuddering. But today the reverse happened, turning on the AC increased engine RPM and stabilized it but turning off the AC lowered RPM and brought back the every 5 second increase/decrease.
As for the oil, it definitely has too much gasoline in it, and as for coolant I feel fairly certain the dark brown swirl is NOT coolant. I was also concerned about how black the old oil was. Since this is the first time and not the last time I have changed the oil, I've always, skeptically, relied on the honesty of the technicians performing the service. There is always the possibility they didn't change the oil and this is actually 20K mile oil. Wouldn't be the first time I caught them charging for parts and labour that were never done.
Several times before I changed the oil, it consistently read LOW and at the very bottom, min, of the scale. I drained 7 litres and filled with 7 litres but it still ready LOW so I added a half litre and the measurement rose a bit. Added an additional half litre for a total of 8 and it finally read OK and about 2/3rds full. Now when I check it, it reads OK but completely full to the top of the scale.
I don’t think 550-600 RPM at idle is too low. It’s just that something seems to be causing your fuel mixture to fluctuate giving you the rough idle - maybe the mixture causes it to dip a little too low as well. Not sure. When you turn on electrical, the engine will normally increase RPMs to compensate for the increased load. Increasing the RPMs will tend to mask the symptoms of the rich/lean mixture.
It would be really good to rule out the MAFs as that seems like low hanging fruit right now. The LR4 puts out data for each sensor as well as a combined flow rate. On my gap tool, it shows “Air flow rate from mass air flow sensor - bank 1” - another for bank 2, then a data field for “mass air flow” which is the combined value. I’m thinking your tool must have the same data fields buried in there someplace. I think the total mass airflow at idle (around 550-600 rpms) should be about 3 g/s at idle, so about 1/2 that on each side. If you could find the fields and record it for a while a graph of the values might show one of the sensors dropping out. Or, like you said, just replace them and see if it fixes it. Not sure if you can get them from a place that would take them back if that’s not the problem - kind of doubt it.
I’m also reminded that we have two sets of o2 sensors - one set on the engine side of the catalytic converter, and one set post-catalytic converter. I think its the first set (pre-cat) that governs the fuel mixture. I assume that’s the set you were viewing. I’d like to run my own for comparison, but my GAP tool is on the fritz right now. Hopefully have it fixed by the weekend.
Another mystery here is that you’re not seeing any diagnostic trouble codes.
I have searched every way I can think of to see 2 MAF sensors and have yet to find it. With the engine running, I did unplug them one at a time. With an idle speed of 625 RPM, the MAF g/s was anywhere from 3-6, after unplugging them, flow jumped to 300 g/s but had no impact on RPM, this was true for both left and right.
Also, idle RPM was not 550-600, it was rhythmically going from 500 to 650 to 500 to 650, on and on. Most of the time idle sits in the low to mid 600s but some times it consistently rests at 700, 800, 900 and sometimes as high as 1100 to 1200. When it is shuddering, RPM is in the 500s although one time I did see it dip even lower.
And yes there are 4 O2 sensors, bank 1 & 2 read the same, 2 of the matching sensors read 1.29, and the other 2 matching sensors read .9 (except when the RPM fluctuation happens, then those sensors would bounce back and forth from .1 to .8 while the others remained constant at 1.29.
I've had main dealer techs have a look over the last 2 years but they've no ideas. I recently had a CAN bus and charging issue and was very confident in my diagnosis of a faulty alternator but JLR shrugged it off and said they had no idea. I replaced the alternator myself and the issue was resolved. I don't really know of any other other techs I'd feel confident in being able to solve this one either.
I'm no trained mechanic, but I've worked on all of my cars successfully, most of which have been Jaguars and I'm an engineer by trade so while I don't have the experience or training, I'm fairly confident in my abilities.
You should follow the below thread. This is the person who seems to be having the same issues as you - he seems to be quite knowledgable. Today, he even mentioned similar issues with his oil. He replaced his MAFs (one looked faulty), but it hasn’t fixed his problems. He’s now looking at the low pressure fuel pump.
Just had another thought connected to the gas in your oil. There have been some engine designs that used HP fuel pumps that would start leaking gas down past the mechanical actuator and into the crankcase. The fuel in the crankcase would then get sucked up through the PCV vent lines and cause the motor to run rich. I don’t know if our LR4’s have a pump that can leak in this manner or not. I know your rail pressure seems okay, but maybe the pumps can still leak down the shaft without losing too much fuel pressure. Wondering what would happen if you disconnected both your PCV lines while you’re having this issue - block the air intake connections so you didn’t have a vacuum leak and just let the crankcase vent to the open air.
If fuel rail pressure appears normal at all times, how do you determine a fuel pump problem especially with the SDD test routine saying the pumps have passed?
I thought about issues with the PCV, though that usually triggers a DTC. I know where they are on the V8, but the V6 seems a bit different and reading through the parts of the workshop manual have yielded nothing with regards to their location.
Two other thoughts, occasionally one of the rigid vacuum lines on the left side of the engine makes a ticking noise and every time I open the gas cap, there is a chuffing/rumble noise from the filler neck, something I've never heard from any other car or current Rover.
Not sure you can directly determine whether the HP fuel pump is leaking, but it might be helpful to know if the gas vapors in your crankcase are causing the rich mixture.
I see you found the PCV, but there are actually two breather lines, one from the PCV valve in the passenger side valve cover that leads to the throttle body, and one from the drivers side valve cover that leads to the air intake. The attached pic highlights the run for each.
I don’t know which rigid vacuum line you’re referring to (or why it would be clicking) - the vacuum line from the vacuum pump along the passenger side of the engine compartment?
One other thing you could check is whether disconnecting the purge valve line from up near the throttle body (and blocking the connection on the throttle body to prevent sucking air) makes any difference in your fuel trims/o2 readings when you’re having the issue. Just wondering if you might be sucking gas fumes from the purge valve.
Left side would be driver's side, and it's the rigid loop next to the the full load breather. Had a read of the other forum thread and it sounds VERY similar to mine.
That sounds like the purge line, and I guess it could be the purge valve clicking. If the purge valve is bad, I think that could be messing with your fuel mixture. Might also have something to do with the pressure in your tank.
