Just backing up a step...when the car is at idle, the LTFT stays steady at around 4-6% (both banks) and the STFT is bouncing around between -25 to +27, without any throttle. When you give it throttle and hold it at around 3K rpms - same result? The STFT still keeps bouncing around while holding RPMs steady?

I’m not familiar with SDD, so I don’t know what those routines are testing. But if fuel pressure is good, the only other thing on the fuel side would be the injectors - which you said checked out (injectors usually give a problem on one bank only anyway - here you have both banks). Then I think you need to look back at ignition or air.

Were the MAFs tested/cleaned?

 

Made some more logs today. LTFT still staying consistently at 4-6%, whether parked or driving about. STFT stayed closer to 0% today compared to yesterday but was still all over the place, negative and positive, whether driving or in park and did have quite a few spikes while parked that would put the total at 15-20% and higher revs putting STFT at 25% +/-. Actual fuel rail pressure was mostly around 20K kPa while driving and 3K when parked, however turning on AC or other electrics, it would go to 13K or higher and stay there, still while parked.

 

LTFT at 4-6% is not too concerning, but the spikes in STFT when sitting parked might be pointing to a problem. Driving about, your STFT will vary - it’s hard to tell much about that without more careful analysis.

Looks like the overall fuel trim trends significantly more positive when accelerating. That would point away from a vacuum leak, which tends to give fuel trims that are higher at idle and lower as RPM increases (vacuum has less effect on fuel mixture at higher RPMs).

The fuel pressure should try to meet whatever the ECM is demanding. The ECM judges how much fuel is need and delivers a pulse to the fuel injectors. When more fuel is needed, a longer pulse is delivered, which requires more fuel pressure. So, as you turn stuff on, the ECM is demanding more fuel pressure.

There should be two parameters in your software for fuel rail pressure - one is for the demanded fuel pressure (from the ECM), and the other is for actual fuel pressure (from the rail pressure sensors). They should be about the same. If the actual pressure is lower than the demanded pressure, this would point to a faulty fuel pump, and the engine tries to compensate by adding fuel trim (longer fuel pulses from the fuel injectors). See if you can get a reading of demanded fuel pressure alongside the actual fuel pressure.

I suppose it could also be the MAFs over-reporting the amount of air (typically I think faulty MAFs under-report). Also could be a boost leak (though not sure why that would affect idle), or maybe faulty boost bypass valve - did you have any work done on the supercharger?

If it were ignition, I would think you’d be seeing some misfire codes. Can you separately pull up data on misfires? Should be stored in the ECM someplace.

You might also want to post-up in the landroverworld forums. There are more people with greater knowledge than me on these topics over there. Seems to be more active with respect to these technical topics.

 

Yes, I didn't have a look at commanded fuel pressure, but will do that tomorrow. No ignition issues or misses recorded or observed. Air filters have been maintained on schedule but I certainly will have a look so as to rule them out without question. I've tried setting up a profile on LandRoverWorld but it always says waiting for verification and I've yet to receive such an email from them even after multiple attempts.

 

Have not really noticed anything of note monitoring data. Performed an oil change today (drain), less than a year old and slightly less than 10K miles on JLR Castrol OE Professional 5W20. Oil was nearly black and reeked of raw gasoline. By the way, when I replaced the spark plugs a couple of months ago, the factory fitted ones all looked perfect with noting unusual. While under the car with the engine running I inspected the pulleys. Everything looked balance and smooth and did not notice any unusual noises. However compared the the supercharger belt tensioner which did NOT move while running, the accessory belt tensioner was moving continuously side to side. Also the rough idle vibration can be heard from the top of the engine meaning the noises the engine makes while running would change accordingly based on how smooth the engine runs. I have noted sometimes when the engine idles smoothly at 850 RPM while parked regardless of what features are turned on or off, but when it idles with shuddering, the RPM is closer to 500-600 RPM.

EDIT: This may be a topic for a new thread, but upon inspection of the oil in day light, it still smells strongly of raw gasoline, and it's definitely black, but not all the way through, there's a swirl when stirred, of a dark brown to dark milk chocolate. Now I've seen oil contaminated with coolant and I couldn't with confidence say this looks anything like that. Also, only managed about 7 litres by the oil pan drain plug, took 8.5 litres to fill it before message centre said level was OK.

 

I think the gas in the oil is almost certainly related to your idle/shudder problems. Could be a number of things, most of which relate somehow to either a leaking injector or a misfire situation, even though you’ve replaced the injectors and don’t see any record of misfires. Could also be worn piston rings, but you don’t seem to be burning too much oil (1L in 10K miles isn’t bad). Either way, need to get that sorted quickly - that much gas will thin the oil and reduce lubricating properties, causing more damage.

The brown swirl in the oil is concerning. I can’t think of anything that would be other than coolant, unless you’re just seeing some crud from the pan mixed up in there - but “chocolate” sounds like coolant. Gas in the oil should not cause a swirling effect - gas is miscible with oil and will thin it rather than separate out giving the swirl. If it’s coolant - again, needs to get fixed before you drive it much as that’s going to reduce the lubricating properties of the oil.

Have you noticed any coolant loss, or increase in smoke from the tailpipes - perhaps on startup or when giving it throttle?

Sounds like maybe the belt tensioner is shot, but with these other issues that would be the last thing on my mind.

One other thing - 8.5L is more than the listed oil capacity (at least on my 2016 model). Should be 8L, and my refill usually takes 7.5L using an extractor pump (so I probably don’t get a complete drain). It usually takes a little while for the oil to drain down and fully register on the electronic dipstick. I would back a little of that out if you have an extractor pump. Especially with gas getting in there, you don’t too much liquid volume or you’ll put too much pressure on the engine seals.

I think you should get this car to a shop for investigation. Take a sample of the old oil to show them. If you’re going to continue investigating on your own, you could test the coolant reservoir for exhaust gas - they sell chemical test kits for this - which would point to a head gasket problem. Maybe also a compression and leakdown test to rule out problems with the headgasket and piston rings. You could send the oil sample for analysis to determine gas/coolant content, but takes a little while to get the results back.

I’d also suggest trying again to get onto the landroverworld.org forum again - make sure to check your junk mail or spam folder for a response. Maybe try the “contact” link at the bottom of the mainpage or email the admin (I think it’s admin@landroverworld.org) if you don’t get a response.

 

Exhaust is normal, never any smoke or soot. Fuel consumption is normal daily 12-14mpg (16-17mpg extended drives) - always has been and most drives are short or involve extended idle periods.

The oil does seem less viscous than new oil by feel. And like I said, I have seen coolant contaminated oil and this oil does NOT look like that so perhaps it is some sort of sediment.

And you are correct, it is 8 litres, I misread the bottle which had measure for quarts.

I'm familiar with the coolant test, but other than numerous coolant leaks for over 2 years, I've not observed any appreciable loss of coolant since the last leak a couple of months ago (and especially since I've fired all 3 main dealers for various failures to perform, I feel my DIY repairs are much more thorough and by the book).

This is my first time ever changing oil as I've always had an unbeatable deal from the main dealer for over 20 years which made DIY changes pointless. SO, my observations are based on ZERO experience with used engine oil. I think the best thing to do is send off a sample of oil for analysis. Not certain how accurate the petrol percentage will be as it sat open overnight but at least it will answer some questions and perhaps provide some guidance as to whether to continue or move on.

Many thanks for the suggestion to contact the admin, definitely no messages lost to spam so something is amiss.

EDIT: Also, all 6 plugs were in perfect condition about 6 months ago when I replaced them with new, nothing abnormal or questionable - so I hope that rules out coil or fuel issues - remember this has been going on for over 2 years...

 

Had the rhythmic 5-second shudder while in park again today for about 20 minutes and noted more data readings. Bank 1 & 2 read essentially the same values. I've recently cleaned both MAF sensors properly again and that still made no difference, air filters have always been maintained so I'm not surprised about that. I understand all is related and perhaps none means anything but this is what I recorded: O2 sensor which normally would read .9 volts kept bouncing back and forth between .1 and .8 volts, RPM kept bouncing back and forth between 500 and 650, STFT kept going from 0.00 to -25.0 and FRP kept going from 3K kPa to 11K kPa. Now this was with AC turned off. If I turned on the AC, RPM would jump up to nearly 700 and stay there and all other values would also stabilize but as soon as the AC was turned off, the 5-sec shudder and bouncing values would return.

Still perplexed why daily idle RPM varies so much. Everything seems very happy when idling between 700-900 and not so happy when idling from 500-600 RPM and occasionally it idles at 1100-1200 RPM, even with electrics turned off.

I've sent off a couple of e-mails to the admin of landroverworld and have had no response.

 

I assume your o2 sensor readings are the same on both sides as well, right?

If both sides of the engine are behaving the same, that would seem to point back to either fuel delivery or air delivery. There are lots of other things that can cause these symptoms, but most should result in some difference between the two banks. For instance, the o2 sensors themselves can go bad - but not usually on both banks at once. The cat converters can go bad, but again - both sides at once? Fuel injectors - same thing. Spark plug/ignition packs - same.

So, assuming you’re seeing the same thing on both sides, it looks like your engine thinks it’s rich and tries to lean out the mixture (that’s the STFT spike to -25%), then the o2 sensor says “too rich” - that’s the 0.9 v spike. The o2 sensor feeds back the rich signal to the ECM, which backs off the fuel, but goes too far giving the 0.1v spike (too lean). This alternating rich/lean cycle gives you the engine surge. But none of this really tells us the cause.

Fuel delivery problems that would affect both banks evenly: the low pressure fuel pump/filter/regulator (I believe it’s a single unit) is the only thing that comes to mind, and they do go bad. But, I would expect this to get worse as you increase throttle. Seems like you should see bucking or weakness under acceleration or high load. The problem should get worse, not better.

Air intake problems - again, the only think I can think of here is a faulty MAF, and I don’t think you can rule this out yet. Although there are two MAFs, the airflow is combined at the throttle body, so a single faulty MAF will mess with your fuel mixture on both sides of the engine. Cleaning a MAF sensor doesn’t work if its crapped out.

Can’t remember if you replaced the MAFs before. Maybe check your MAF airflow readings on both sides of the engine when you’re getting this problem. They should be about equal. There was someone on the other forum who just had a MAF go bad a week or so ago, so this is not uncommon. His symptoms were not as bad, but he was having idle issues and bogging a bit when he came to a stop, and his fuel trims and o2 readings were off (but your spikes are much worse). MAF sensor readings showed one of his sensors was dropping off periodically - showed up when coasting, but it might have been a coincidence - a faulty MAF can cut in and out randomly.

I’m just going to throw this in here as well - I’m not a mechanic; this is just a hobby. I’m worried about your oil having so much gas in it, and possibly even coolant. I would suggest not driving this car much until you sort this out, or having it checked out at a garage before you do real damage to the engine.

 

One other thing - I think those fuel rail pressures are about what I see. Around 3K for normal idle, and it ramps up to 11K or so at 650.