So this is an escalation of my problems.

car will now not hold idle.
driving to work today and idle dropped low every time i took foot off accelerator. Had to hold down accel while stopping/stopped all the time.

(trans light came on cus engine speed v wheel speed)

now i have no idea.
My only thought left is ecu or internal engine damage.

have replaced parts, checked parts.
at a loss.

when starting the last 2 days i have had to hold accel down a little to get it to run.


fuel pressure seems to be ok.
so why is it not getting enough fuel or air?

doubt its spark cus the idle is not jumpy like a miss.

Wrote something but a screen scrapper pirate took over this webpage , webpage itself and I lost my reply , *%^%#^*$!@)&#*%$@^*$

Will try again in morning

You're driving on 5 cylinders, I can hear it in the second video, just a matter of finding why and what's causing it but my guess is dead coil? You need to check obd live data, might give you some pointers but wont show dead coil.

no indication that i can see.
and what makes it more bizzare.

yesterday morning drove to work = ****.
drove home = perfect

this morning drove to work = **** (as per video)
this afternoon drove home = perfect as if there was never an issue.

i have obd fusion set up in car. Not sure what to look for that may point me at the right thing.
interesting tho that rpm seems smooth tho yeah?
Would have thought loss of idle would make rpm jumpy.

how would i go about checking coils?

Removed coils one by one.
in this video you can hear/see idle change and hear the coils arcing as removed.

if i disable my bonnet light i can see arcing if i put it near the engine.
(unable to record the arcing tho)

Opposite of what i have been used to seeing for the last year.

stft showing very lean condition.
idling well whilst showing lean though.

I don't think there is a reliable way to test partially faulty coil without simply swapping it for a good one, if you don't have a spare or two I'd recommend getting a couple, that way you'll be able to quickly find if it is actually dying coil.
It can however be also a stuck or dead injector, you could also check compression just to be sure it's all fine.
That 2nd video from your first post, when you accelerating, car sounds like a train, that's basically how it sounds when it dropped a cylinder.
As for obd live data, just make sure that all data looks ok, tps voltage, that oxygen sensors are in closed loop, cts temp showing correct value, show us a screenshot if you're unsure of anything.

Vee's IAC valve exersize / reset

EGR valve seat cleaning and EGR_ERROR ......PID on a ELM - 327 device

Your cracked exhaust manifolds / leaking donut gaskets would show rich at idle and then on throttle up my be unburnt fuel in cylinder mucking things up

EVAP valve under battery may not be inially closed , a 9 volt battery will make it click , check for vac line on under intake manifold about cylinder 2 0r 3 , mine was missing , you can cap the vac line for test

banjo fitting for the power assist brakes on the top of the valve cover , tricky in how it is remove and the hole can be plugged with childen's model clay at the dollar / pound store

I would bet on MAF failure. Recently i had the problem car just stalling when run steady on highway like misfiring, then it starts drop the idle when sitting in traffic, then it dies when i shift from d to r and back, then bad start on hot like fires right away and then dies and it took like 3-4 tries to make it run and then bad cold start same way. And all of this kinda erratic like this or that or two or all. And it always felt like very bad misfire over and over while i was trying hard to pinpoint it with plugs, coils, IAC, throttle position, fuel pressure, EGR, etc. Until i messed up and occasionally didn't connect the MAF and the car started and run in limp but run rather good. People said Range Rover P38 4.0 MAF is same and it is much cheaper so i found one lightly used like for $50 (had same marks as mine except RR part# on it), drilled out the rivet mounts and replace mine securing it with suitable self-tapping screws. Complete RR assembly does fit too but sensor is under different angle so the harness reaches it very tight. Since then i've got the car running smooth at all ways with better overall performance and economy.

have done the IACV test and shows it can move.
have also removed and put a larger gasket spacer in place and the car has adjusted for that and idles as expected.
i have purchased another cheapo china special tho and will happily swap as its only $20

i know i can't expect perfection with the exhaust manifolds as they are.
the crack is only small.
i have patched up the best i can and the leak is reduced compared to what it was.
also cracked exhaust manifold should only cause issue once car has switched after it has warmed up and begins using 02 sensors.
on cold start it should be an irrelevant factor.

i am pretty sure i have checked all vacuum lines.
i have used some rtv and stopped some intake leaks around the brake booster on the inlet manifold and also another fitting that was on top a little further back.
smoke machine now shows no leaks on intake.

maf voltage tested and working.
obd shows expected readings on maf
also swapped for another assumed working and no difference.
unplug maf and car struggles to run.
all signs point to maf being OK.

i disconnected the 2 air recirculation lines from the exhaust manifold and plugged them up as that would have been pushing rich exhaust gasses back into the intake making the car run even richer.
that may have potentially shifted the car from always running very rich to now having idle at lean condition.

on the weekend i switched the ECU back to the one that was originally in the car. (was swapped out after i first began having stalling issues. initially seemed to fix but then have since come back.)
first couple starts it was a bit rough but after a few it seems to run well.
have not had the chance to take it for a drive.
maybe on friday I will start it up in the cold morning and take it for a drive and see how it goes.

i think at this point i have checked/tested/cleaned and/or swappped everything.
MAF checked and tested.
IACV checked and tested.
Fuel pressure regulator swapped and installed fuel pressure guage and have good pressure.
O2 sensor are only a couple of years and maybe 20000km old.
TPS checked and tested.
Throttle body fully cleaned.
Air filter replaced.
Air inlet pipe all cleaned.
Coolant temp sensor changed maybe 2 years and 30000km ago.
Inlet air temp sensor changed just on the weekend (old one tested and appeared ok)
CKPS changed.
Spark plugs changed (with dielectric grease applied)
Ign coils tested. (new boots also installed on them)
fuel injectors fully cleaned, new micro filters and o rings installed.
fuel rail also cleaned a that time.
also as mentioned smoke checked for inlet air leaks and sealed up any with RTV
reduced exhaust leaks as much as possible without replacing exhaust manifiold

irrelevant but also recently installed 2nd hand alternator.
and changed both front belts.
thermostat also swapped with fairly new 2nd hand but fully tested unit. (for those that remember the issue i had with the cat not warming up)
also recently re done valve cover gaskets and ensure no oil leaking into spark plug wells

I see only two possible outcomes here.

A clogged filter sock at the fuel pump. When cold, fuel can seep through the filter sock to get to the pump. Eventually, the sock gets overloaded and can't continue to provide the fuel to the pump. This is why the fuel pressure tests well. I you can watch the pressure when the failure occurs, you would be able to know for sure, but this has happened to at least one other person on these forums.

The other is a failing ECU, which I think is significantly less likely, but certainly easier to cross off the list.

I don't think there's any way a cracked exhaust manifold can cause this problem. You are right to ignore that.

I think if the fuel socks were clogged, he couldn't manually put his foot on the gas and get it to rev back up. But you can take a look in the gas tank quick to see.

Is it possibly a damaged wire or bit of loom? Seems like you've checked everything.

certainly have checked everything.
i have done my best to check wiring and can't see anything.
I just swapped back the ecu to the one that was previously in there along with putting another new (aliexpress special) IACV.
so far it seems to be runing well but only taken it a short drive and had it idling in the driveway.
it really does come across as an intermittent issue and everything itself seems to check out.

I am as sure as i possibly can be that it is electrical.
be it wiring or maybe some bad solders inside ECU.

if i get it running well again i just hope it stays that way.

You either haven't or just not letting us know what and how you done it. From a reader perspective you just fired a parts cannon at it and hoped for the best.

MAF checked and tested - how you checked and tested it?
IACV checked and tested. - how you checked and tested it? Is it original Jag part or generic replacement which are known to cause some issues as the plunger shape/iacv orientation can be/is different.
Fuel pressure regulator swapped and installed fuel pressure guage and have good pressure. - even with the gauge installed and decent pressure you can have a flow issue which wont show at a gauge.
O2 sensor are only a couple of years and maybe 20000km old. - you haven't confirmed if they are running in closed loop, you've not shown any obd data.
TPS checked and tested - how you checked and tested it?
Throttle body fully cleaned. - cleaning it is meaningless if you don't set it up correctly afterwards which is a rather involved but wouldn't cause your issue
Air filter replaced.
Air inlet pipe all cleaned.
Coolant temp sensor changed maybe 2 years and 30000km ago. - does it show correct values under OBD?
Inlet air temp sensor changed just on the weekend (old one tested and appeared ok) - this also shows under OBD but doesn't have any effect on the car whatsoever, whether it shows correct temp or minus 80C.
CKPS changed. - irrelevant here.
Spark plugs changed (with dielectric grease applied) - only champions or NGK spark plugs are recommended for your car. Bosch are known to cause all sorts of issues.
Ign coils tested. (new boots also installed on them) - as I told you, there is no reliable way to test these coils, you'd have to have a scope set up and observe trigger and spark while the car misbehaves which would be rather hard to achieve.
fuel injectors fully cleaned, new micro filters and o rings installed. - could still technically be a leaky or partially stuck injector but very much unlikely
fuel rail also cleaned a that time.
also as mentioned smoke checked for inlet air leaks and sealed up any with RTV
reduced exhaust leaks as much as possible without replacing exhaust manifiold - this also wont cause your issue.

My recommendation stays the same, your video shows car that dropped a cylinder, you could check compression but 90% of these cases are down to failing coils, they really are the worst part on these cars, swap a coil or two at a time and test. If you want further help, replace coils and/or provide OBD live data, otherwise its just a guessing game/parts cannon scenario.

Sorry if my reply comes off wrong but your reply here reads very poorly to me. it reads more as an attack than as any suggesting.
as opposed to asking questions you are seeming to imply more that i have not done things properly and am not sharing information.

this has been an evolving issue posted in other threads as i thought the issue came and then went.
i am sure you have commented on some of that also.
i deliberately included the extensive list of what i have checked/tested/replaced in this thread to try and help keep it clean to say YES I HAVE DONE THAT so i don't just keep getting the same over and over again, "replace o2 sensors" or "check fuel pressure" or "check MAF" or similar.
i have shared plenty of videos that show my obd data in other threads. and i can share more here.
via the obd fusion app on my head unit.
i just have not put any here as there is nothing to report from it and it is nothing new.
at what point tho does it look like any parts cannon was fired?
not that many parts have been changed at all.
and in fairness parts were only changed due to having another car.

-maf has been voltage tested as have been shown what voltages to look for and the OBD shows it is reading correctly.
-IACV was taken out, cleaned, run through a test procedure to show that it can open and close. and verified as doing so by the fact that the idle does change and could be manually set to any idle i wanted by physically making it any length and leaving it unplugged.
- if there is a fuel flow issue then pressure will be affected. pressure would not be right if flow is not there. would either be too low or too high. i can't see how any other way.
- car does enter closed loop. can see on obd
- TPS has been voltage tested and also can be shown in OBD to read from 11% at idle to 96% at WOT.
- TPS has been cleaned and has been re calibrated.
- coolant temp does infact show correct values.
- inlet air temp i was hesitant to change, the values it was showing previously were slightly wrong so that is why i changed it i was told it did infact affect the cars running and it makes sense given hot and cold air has different density.
now it could just be coincidence but since changing it the car has behaved better.
- spark plugs changed, yes of course with di-electric grease and the correct champion plugs
- ignition coils have been tested as best as i can, and without as you say throwing a parts cannon at it there is nothing more i can do. and i really can't see any scenario in which the car is missing. i have looked, my brother ( a mechanic) and 2 other mechanics have had the car for various issues and no one has seen anything that appears to be a mis fire by any means. currently my spare parts car is misfiring and will not hold idle so i have that point of reference and also can not trust any coils from that car at this point thats for sure.
- yes technically a fuel filter could be blocked or whatever but when they are cleaned and tested well what else can be done? (aside from throwing the parts cannon and spending a tonne of cash on new injectors when all indication points to these being fine)

as things like sealing exhaust leaks, that won't cause the issue things like these were something that was done as
A - it can't hurt to do it,
B - everything you can tick off as good makes trouble shooting easier.
C - whilst having exhaust leaks and knowing fuel trims are going to be affected it makes one piece of data less reliable than it needs to be.

next time i take the car for a drive i will take some more live OBD2 data recording.
i am somewhat confident that it will be ok as i have assumed all along i think i have had a combination of issues.
for example
i know i had leaky fuel injectors, but prior to repairing those i swapped the ECU (because i had a spare) when i swapped the ECU it started to run better but then got worse again.
fixed the fuel injectors, it started to run better but then got worse again.
i feel this may be due to infact the initial issue being incorrectly solved by an ecu swap that has just not helped in the long run.
now putting the original ecu back the car seems to be happier.

just to add the amount of hours i have put in trying to work on it and testing things in a deliberate attempt to avoid buying parts is a lot.
it is only small sensors and serviceable items i have purchased. which all are fair enough to change anyway on a 30yo 370000km car

Should have probably started with that when asking for help. No one here has a crystal ball, neither we have seen your car in person, prior to last post your troubleshooting just looked like a parts cannon without understanding the problem. It is what it is.
Your OBD data looks fine now but then the car also currently runs ok, your MAF showing a bit low, think the lowest I've ever seen was always 0.2 on a healthy MAF but that might be a red herring. Voltages at different RPMs directly at MAF would probably be a better idea, I'm sure I've seen an operating voltage table for the MAF on this forum.
You'll also need to capture the OBD when the car runs poorly.
Your troubleshooting of the coils is misleading, like I said, you can't really test them and with majority of running issues being down to coils, that would still be my first call.
Basically any running issues on X300 are down to:
1. Coils
2. Go back to point 1
3. Only at this stage consider other things.
Re fuel flow, when the car runs poorly, you can try simply pinching return line, that should tell you if there's anything wrong with the fuel flow. Can't really rely on the fuel pressure gauge, I know, I've tried and ended up replacing fuel filter to fix the flow issue and the bogging down. While there I had a pressure gauge in and never had anything else but textbook pressure.
IAT makes no difference to how the car runs, I know, I've been running mine for a few years, showing minus 40C or more in the summer before eventually replacing it. Never even triggered any errors nor it caused any erratic fuel consumption.
I'd also check compression, just to be sure, you don't need any new parts to do that and as your initial video shows you were running on 5 cylinders.

I can confirm that the coils are impossible to test without specific tools.

Also can confirm that IAT will not cause a car to stall out. It makes minor changes to fueling.

like i said this is part of an ongoing issue and yes lots of data has been shown. I have spent far more time troubleshooting to no avail than anything else.

Sorry that you have missed all that but no need to be so presumptuous when people come to share stories and ask for some help. I appreciate all help of course but how you get parts cannon from anything i said i can not understand. Nothing but a few serviceable parts have been replaced.
except for ecu because i happened to have a spare.

I will record as i drive.
and the maf reading may seem a little low i understand. I think that is just obd.
when i did a voltage test and ran it through rev range it all matched where it should

i understand what you are saying bout not being able to test coils.
and that just sucks as i can not afford to buy spares and throw parts cannon at it to try and maybe come up with nothing. I don’t see how it is missing tho.
i understand what you might be saying bout the second video but of course it runs like a bag of **** regardless if fuel, air or spark.
I can try with old coils from my parts car but i don’t know if any of those coils are any good either as that car won’t even hold idle it misses so bad

Biggest problem with intermittent issue is never knowing if what you have done has fixed the problem or if it is just going to show again in time.