After checking over everything again electrically, I decided to go back to basics and do a compression test...

Cylinder 1 has zero compression, cylinders 3, 5, 7 all had around 155psi (not the highest I suppose, but consistent and even).
I checked 4 out of interest, and that had 150ish

So the issue is with cylinder 1, I got so lost in thinking it was an electrical issue, I wish I had tested the basics like compression earlier on. Although one of the old coil packs was bad, so at least I found that in the process.

So intake back off, rocker cover back off and I can't see anything wrong. The push rods all feel the same, they are all sitting in the lifters, I removed the rocker assembly and the arms rotate freely across all 8.
I can't see it being the head gasket, as that was replaced in the rebuild a few years ago and it's only had little use since and no overheating or pressuring the coolant.
I can't imagine it's a slipped or cracked liner as it was running fine before the rocker assembly was changed, plus would that be able to give 0psi compression?
So I guess it must be either a dodgy lifter or one of the valves?
It's looking like the whole head is going to have to come off again 😞

I feel like if it was a preload issue, I'd see some sort of issue on the other cylinders? As I guess it would be pretty rare for preload to only impact one cylinder so drastically?

Any ideas or other things to test?

Hmm, that is true!

It's a Bosch MAF, I can't remember when I fitted it now, but has been fine previously. I'll check the wiring to it tomorrow and take a look at the values it reads with the Nanocom.
Although I guess if it was the MAF it would be more likely to effect all cylinders, rather than the weird 2 on each bank.
I'm going to check the readings from the lambda sensors tomorrow too, although if it was these, I'd expect one bank to be running rough.

I just can't understand it still, I want to doubt the roughness readings and which cylinders this shows up on, but I can't see how it would detect roughness on the wrong cylinders all the time.

Just spent another few hours on this. I removed the coil packs again so that I could clean up the bracket and put all the bolts in, as I decided with everything else changed, it must be an issue with the grounding.
I removed the coil packs from the bracket and thoroughly cleaned them up, using a Dremel to gently sand the rust and dirt off the surface, especially where the coil packs touch the bracket and where the bracket touches the intake manifold and bolts. They were pretty crusty and probably not providing a great ground.
Then I cleaned the threads for the coil back bolts and replaced all of them with brand new bolts. I'm not sure why it seems that when looking online, originally Land Rover only used 3 bolts per coil pack, when there are 4 threads. I put all 4 in per coil pack. Previously it only had 2 per coil and has been like that since I bought the car.
I tested all the resistance again - the primary on all coils was 0.4 ohm exactly and the secondary was around 11k on all with no leads connected.
I put everything back together again and started it up - initially it was showing roughness on 1, 4 and 8... However after a few minutes and letting it idle for a bit it went back to the usual roughness on 1, 4, 6, 7 - with the roughness being progressively worse from 7 towards 1.

Next I tried running it with the MAF disconnected, but that didn't make any difference.

So then I made up a short 3 pin male to female jumper cable to sit between the loom and the coil pack. I cut in 12v on the centre pin and used the original loom with the short little bypass cable to provide the switched ground. Exactly the same :(

Sometimes it struggled to start, other times it was okay. I'm not sure if that points to issues with the crank sensor though or rather just that some of the cylinders are filling with fuel and it's not burning.

I struggle to think it's MAF, crank sensor, cam sensor etc related, when it shows that it's always the same 4 cylinders with issues and they are all related to one of the coil packs.
I'm also doubting the lambda sensors, but then that doesn't make sense either, as it's 2 cylinders per bank, not all on one bank.

Errors today are just P1000, P0301 and P0300

I've been cycling through the different inputs on the Nanocom and of course the fuel trim is a bit of a mess and the only other one that stands out is target engine speed being 3000rpm at idle... That doesn't seem right.

I've been resetting the adaptive values between each run and also the battery was fully charged with my trickle charger before I started, to make sure it was kept topped up and low voltage would not cause any issues.

At this point I'm completely out of ideas. I'm debating having to take it to someone else.

Yeah, both brand new, I went for Allmakes ones, as didn't really want to try Britpart. I checked the resistance on each coil before install and they were all around 13k secondary resistance. I double checked again yesterday across the coil for 1 and 6, but through the ignition leads to save trying to reach down to the actual coils. It was around 14k, which seems fine considering the leads were in the chain too.

Yeah I did, I've got both new coil packs on, new leads on all plugs and all new NGK spark plugs.
The new coil packs were all about 13k when I checked them before install last week.

The part that makes me think it's neither the crank or cam sensor is the fact that it's so predominant on the 4 cylinders from the same coil pack, even if it seems to not be 100% only these cylinders today.

I'll have a look and check the wiring to the cam sensor, as I can't remember exactly the route that takes right now, I think that is lower down, rather than by the intakes/top of the engine, so not likely been disturbed, but worth double checking.

I've been thinking all week about this and searching online for any other ideas. I checked the coil packs that I had removed and the secondary resistance on the coil for 4 and 7 reads around 3.3M ohm, whilst 1 and 6 was a touch under 13k and the other 2 coils on the other pack were both a touch over 13k ohm. So there clearly was an issue with that coil, which made me think maybe some damage had happened to the ECU from such high resistance. I concluded it may well be ECU related and ended up ordering a Thor ECU on Thursday for Friday delivery.

I've just tried the other ECU, after setting the immobiliser code and clearing the adaptive values again. Sadly the same. Although, if I sit and let it run I'm seeing random roughness on the other cylinders a little more too. It's only logging misfires on cylinder 1 and occasionally cylinder 4. If I rev it to 2000rpm it stops the misfire count increasing until it drops back to idle again. Although it doesn't sound smooth when holding around 2000rpm, it feels a little better, but still sounds like it's running rough. As it warms up it runs a little worse than first cold start though. I let it warm up until it auto switched to LPG and it didn't affect how it was running when it switched.
Looking over the wiring loom again, the only other sensor near by is the crank position sensor really. I've just looked at the pin out of this to the ECU and tested for continuity or shorts and then also tested between pin 46 and pin 35 on the connector that goes into the ECU whilst the position sensor is connected and get 0.9k ohm - which from checking online appears correct for a good sensor.
However the other random cylinder roughness today is making me think it could in fact be the crank sensor going bad, as at this point I've replaced every other component for spark. A couple of times the roughness would settle down to just show on 1 and 4, before then randomly showing on other cylinders as well. Cylinder 8 seemed to run rough for a few seconds and then be fine, intermittently.

After all the test running, I checked for fault codes and there were none logged for misfires, just codes Pxxxx Permanent voltage supply fault drive cycle A, occured 1 times, signal too low, not currently present and P1000 Lambda sensor upstream catalyst bank 2, drive cycle C, occured 1 times, signal invalid, fault not currently present.

It's so frustrating, as I can't seem to get any closer to finding the issue and I just want my car back now!

Yeah, to be honest I never really thought about it last time I replaced them, as I just went for the same again. I suspect the heads were replaced before I got it. I bought a fully refurbished set from V8 developments the other year and they are the same, enough space for a 21mm spark plug socket.
I ended up keeping the other heads, as I plan at some point to get them skimmed and maybe one day build up a fully reconditioned engine from a top hat block.

That's really kind Richard, let me have a think too this week and see if I can come up with anything else to test or progress any further in diagnosing and I'll let you know if it's time to give the ECU a test swap.

Thanks Richard.

I found a 3 pin connector the same as used on the coils, in my spares box. So I quickly soldered up a bit of multi core cable to it, then cut the 2x switched ground wires at the ECU and connected them up to the multi core. Then gave it 12v on the centre pin, just directly to the battery to test.

Again, reset the adaptive values and started it up. Exactly the same. :( So I re-soldered at the ECU end and switched back to the actual engine loom.

I've just run it again and initially when you first start it, it's not quite as bad. However as soon as the revs drop back down to idle under 1000rpm, the full roughness and misfires on cylinder 1 are more apparent. Still the occasional misfire on cylinder 4 too. However today it seems the misfires are not enough to trigger the fault codes, despite seeing them on the live inputs page of the Nanocom.

The new spark plugs have done something, as actually cylinder 1 roughness settled down to 8-9, rather than the 12 I was seeing the other day. I used to have Bosch spark plugs, only because it had them when I bought it and they seemed to work well, so when I replaced them previously, I just bought the same ones again. This time I went for the NGK (the 16mm ones, although the Bosch were 21mm and always fitted fine) as recommended by many with these engines.

I agree, it has to be related to the work I did. However I've run out of options really on what to try next. I also find it highly unlikely to be an ECU issue, that's suddenly appeared coincidentally. If it was all on one bank, I'd say something else got messed up, but the fact it's also on cylinder 4 and 6, which haven't been touched at all (well before I started replacing the leads, coils and spark plugs of course), it seems to be spark/coil related.

I've triple checked every connection that has been unplugged, tested pin outs for continuity and shorts etc multiple times now. Going to have another think what else to test.

So another update. I bought new coils and leads, as I was pretty confident it was the coil pack and decided I'd rather have a spare to swap straight away, than to take one out and then have to wait for a replacement to arrive. Also if I was buying 1 coil pack, I may as well buy 2 and new leads, then it's done properly, knowing that they are a bit of a pain to get to and bolt in (Plus I had no idea what brand or age the current ones were).

So swapped to the new coils on the bracket, but found they only had 2 bolts in each coil, but they are about 30mm long M5 bolts and I only had shorter M5 bolts, so had to leave them with just 2 in each coil (in opposite corners). I'll get some longer M5 bolts so I can fix them properly. I did however buy new bolts for the coil bracket, so that I could fix the bracket to the engine properly with all 4 bolts. I also put the full set of new leads on.

Rebuilt it all, cleared the faults and reset the adaptive values, then started it up, initially it felt smoother, but after 30-60 seconds it started to feel rough again (although not quite as bad as before). I checked with the Nanocom and the roughness timing was like before, high on cylinder 1, not good on 4 and 6 either, but lower values and the a little roughness on 7. Misfires were showing on 1 and a couple on 4.
I checked the faults after this and P0300 and P0301 are back.

It's so annoying, it has to be coil pack related, for it to be across both banks, but only on one coil of cylinders. However it's not the coil pack, it's not the leads and whilst I was pretty sure it wasn't the spark plugs, I bought a new set of NGK, as the current ones have been in for a while now. I've just managed to swap all the spark plugs over this evening, reset the errors and adaptive values again and started it up - it's ever so slightly less rough, but still far from right. If I rev it a little it goes a bit smoother, but it's still not right.

It's also quite clear from the roughness values that it's worse on the furthest away cylinders and therefore longer leads, than it is on the closer cylinders. I'm convinced it's electrical, but can't determine where, as both coil packs have 12v on ignition and the 2 switched ground pins per coil pack have continuity back to the ECU plug.
I'm thinking next step is to get another 3 pin connector for the problematic coil pack and bypass the main loom, connecting it straight back to the ECU pins.

Oh and I also pulled the fuse to the LPG setup and started it up again, to rule out the LPG ECU doing anything weird to the injectors. That didn't change anything, it still gave the same roughness values and poor running. Though I really don't think it's injector related anymore, as I've tested them with an LED and you can smell the fuel. It's definitely got to be an ignition/spark issue, from the passenger side coil pack.

The Nanocom roughness values are approximately:
Cyl 1 - range from 8 to 10
Cyl 4 - range from 3 to 7
Cyl 6 - range from 2 to 5
Cyl 7 - range from 0 to 2

The other cylinders very occasionally show a number other than 0, but so quickly and always 0.something - so I think that's just anomalies.

Any other ideas?

Actually ignore the centre pin bit, the centre pin is ignition switched 12v of course and easy enough to test...
I've just checked and that is showing 12v once the ignition is on.
So that rules out the wiring to the coil pack.

Finally had chance to do some testing today. I lifted the intake manifold again, as I couldn't get into the injectors on either side to get a reliable connection. I put an led on 1 and 3, then put the spark tester inline on cylinder 1.

Before I started it up, I reset the errors and adaptive values (decided that the adaptive values would be a mess after last week's testing).

It fired up, but was immediately rough. I checked the LEDs and both were blinking as I'd expect. The spark tester was also blinking. I checked the nanocom and the roughness timing was extremely high for cylinder 1, plus not good on 4 and 6 (but not quite as high numbers). 7 was also not great. Occasionally 8 would show a little roughness, but not anything like the others and I'm not sure how the nanocom measures the roughness on each cylinder exactly, so maybe an anomaly?

I then moved the spark tester to cylinder 3 and started it up again. The tested looked similar?! I'm not sure, the red light is pretty dim on both, so not really great for testing.

However cylinders 1, 4, 6, 7 are all on the same coil pack side...
I tested the 3 pin connector again for continuity back to the ECU. The 2 outer pins, are fine, both go to the same connector block on the ECU (but different pins of course and there is no short across the pins). Where does the center pin go to?

Either way, it's something coil pack related, maybe the coil pack is failing? It's doing something for the spark tester to light up, but it surely has to be related to this, based on the cylinder numbers with issues. It doesn't sound nice at all when it's running.

The nanocom shows errors P0300 and P0301, the live misfire input aligns with that as there are a lot of misfires on cylinder 1 and occasionally a couple on cylinder 4, but seems to be not enough to trigger the fault code.

Can the coil packs become weak? Looks like it's time for new coil packs... Any way to test them, if I remove them?

Oh that's a good idea! I do have some 3mm LEDs and resistors, so can try this on the injectors!
I can wedge one in both injectors 1 and 3 at the same time and compare.

I've also just found my spark plug tester, just one of those cheap inline ones, but at least I can check these too now.

Will have a look at it all later and see what I can find.

Thanks Richard!

Thanks, really appreciate all your knowledge!

You're right it was actually P0303 for cylinder 3. I think P1313 was amongst the previous days errors, but I stupidly forgot to save or note the error codes before I cleared them! P0300, P0301 and P0304 were definitely there the day before.

Ahh, okay that makes sense now, the ground is used on the coils to switch the spark and 12v is live at all times (well with ignition on). That explains why there was no continuity between any of the 3 pins and the metal plate that holds the coil packs. I was for some reason expecting there to be a constant ground and the other 2 pins would be +12v for switching the coils to control the spark.
There has only ever been one bolt holding the coil pack plate to the inlet manifold and even that isn't the correct bolt... I really need to find what size they are so I can secure the coil pack plate properly.

Yes, there is a grey 3 pin connector to the idle air valve, that comes from a smaller branch of the loom that has this, the throttle body sensor connector and one to the purge valve.
I cheated when I removed the inlet manifold and didn't actually disconnect the coil packs. I didn't fully remove the manifold, I just disconnected enough to be able to move it up slightly and give enough clearance to get the passenger side rocker cover off. That meant the coil packs stayed connected just pushed back enough to not prevent the manifold from lifting up.

Also correct with the LPG wiring, there is a wire spliced into the +12v at petrol injector 1 that is used for the ignition 12v to the LPG ECU. I'm not sure where the RPM wire is, I didn't pay attention to that to be honest today.
All the injectors negative feeds have been cut and go via 2 connection plugs to the LPG ECU. To make it extra annoying, the wiring hasn't been crimped directly into these plugs, but soldered on to pre-crimped wires in the plugs, which use different colour wires! So the wire colours change multiple times!

It's a mystery, I convinced myself it was an injector wiring issue, with something shorting, but apparently not.
All the ignition leads were new when I did the head gaskets and rebuild the other year. The coil packs I don't know how old they are, as I've never replaced them, but have always been okay.
The MAF I've also replaced with a new Bosch one a few years ago. What's so annoying is other than the new tick noise, it's been running really nicely. No misfires on LPG or petrol, decent MPG (about 20mpg on LPG on a longer run) and idled smoothly on both LPG and petrol too.
So frustrating :( Something relatively simple has turned into this!

Thanks Richard, I've been working through the wiring to the injectors, coils etc today. It's been a long process of carefully removing old insulation tape and messy wiring from whoever fitted the LPG conversion years ago.

Does anyone know the pin out for the connectors into the sides of the coil packs? (The 3 pin connections into the main engine loom). I'm trying to trace these now, but struggling to find the details in rave. I've found the connector (C0156) for coil pack 1, but I can't find which pin leads to where in the loom.

Edit:
Should the coil pack be grounded via the connectors or is the grounding purely from the screws to the inlet manifold?

Yesterday after the initial start, it really struggled to start again, it was running so roughly and would barely turn over. It smells of unburned petrol. So today I focused on the injector wiring, knowing these had been cut previously for the LPG install. I found one break in the insulation on one of the negative wires to the injector for cylinder 8, which may have been able to touch the air inlet manifold and short to ground.
Other than that I couldn't find any problems, so put the inlet manifold, maf and intake pipes etc back on and started it again. It turned over better than yesterday but was rough, initially the Nanocom wasn't showing any misfires, but you could feel and hear the misfires through the vibration from the engine. Shortly after it was showing misfires again on cylinders 1 and 4.

Yesterday I'd cleared the errors on the ecu, so today it was a fresh start. I got error P0300 for misfires and weirdly P1303 for cylinder 3 misfires... Yesterday it was errors for cylinder 1 and 4.
Along with the random misfires on all cylinders yesterday, it's making me think it's not specifically only 1 and 4, it's just they seem to be worse.
It must be wiring related, but I just don't know what or where, all the wiring around the injectors and the manifold that has been removed looks okay and from testing continuity from various places like the LPG install connectors back to injectors etc seems to be okay. The 12v feed to all injectors appears okay too, running back to the engine ecu connection block. The injectors themselves are all showing around 14ohms of resistance, when tested individually.

Hmm, so an update to mine, I bought another rocker assembly set, so that I had spares of everything before I disassembled the rocker cover again. I found that one of the push rods spins freely on one rocker. When I look at the rocker it's not easily visible any damage really, but I suspect the ball head is slightly recessed. I swapped over to a full new shaft and rockers, as well as all new rods. All the rods are now firm and feel secure.

I started it up and it had an awful misfire. I plugged the nanocom in and it's misfiring on both cylinder 1 and 4, plus a few random misfires on other cylinders. It was fine before... I've just taken the rocker cover back off and run the engine with it off to check everything over. It seems okay, oil is pumping nicely and although it's not had chance to warm up there is no noticable tick. However the misfires are a new issue. It seems it can't be directly related, as cylinder 4 is on the opposite bank that I've not touched. I'm wondering if I damaged a wiring loom or what now... Any ideas where to start?

Yeah that's the thing, at some point the car had a replacement engine, a number of years before I owned it. There is a receipt for engine replacement and labour, but no details on what it actually truly included or age/mileage of it. So no idea what the age is of the rockers.

When I stripped it down the other year I was pleasantly surprised by how clean it was under the valley cover and since the reconditioned heads and new camshaft went in, overall it's a really clean engine on the inside. In fact when I took the rocker cover off yesterday the heads look brand new still. I've only done probably 6k miles since the rebuild work and I run 90% on LPG and keep oil changes strictly to yearly.
That said the rocker arms and shafts are probably the most used looking parts now internally, at least top end side of things.

Yeah the other noise I've really stopped worrying about, I'm not fully convinced it's the gearbox to be honest, I always feel like the noise comes from further forward, so really not sure what the cause is and not too bothered anymore.
This new noise is more concerning, as it can be heard clearly with the bonnet shut and pretty loudly.

I shall take the rockers back out and inspect more closely over the next few days and decide where to go from there.

I suppose I worry too much about liners whenever I hear any noise :/

Thanks Richard!

Well I use 10w-40, to be honest I always have and it's been fine, then I bought a couple of bottles earlier in the year in preparation for the next oil change as usual. Since the tapping started I've been reading about 10w-60, which if I didn't already have the 10w-40, I'd have given it a go this time.

When I rebuilt it, I stupidly decided not to test the preload and therefore didn't use any shims. I guess once I put everything back together and everything was running fine and quiet, I thought I'd not need to bother with shims. Since the rebuild which was I think about 3 years ago now, everything has been fine, no ticking, no coolant or oil use etc. The other noise that I've posted about before is lower down and I asked a Land Rover independent specialist (reluctantly had my ball joints done there, as I didn't have the time last year or tools to do them myself) and at first they said what noise, which is reassuring that it's a common thing with these V8s and then when I pointed it out, they reckon it is more likely from the gearbox and nothing to worry about, just a typical noise that some have.

I've been searching around online this morning and seen a few different people that had issues with the cups in the rockers being loose or excessively worn. Yesterday I was more focused on the pads and rockers themselves than the cups where the push rods sit.

I think I need to take the rocker cover back off and look deeper at the cups of the rockers and the rocker shaft.
Seen as most other things have been replaced over the last few years, maybe it's time to go for new rocker arms and shafts, as well as new push rods. Then I can at least rule them out and test the preload and install shims if needed.
Should I choose to go down the route of new rockers, what rockers have others opted for? Not so keen on the idea of Britpart ones, but looks like there aren't many options...

Hi all,

It's a while since I've been on here, the P38 has had a few bits done here and there, like blend motors, but in general for the last couple of years it's all be fine.

A couple of weeks ago I noticed a new ticking noise. It seems to be from the passenger side, it's not there when you first start the engine from cold, but starts after a couple of minutes, once it warms up.

A few years ago I partly stripped the engine down, to replace head gaskets, camshaft, lifters, etc and installed reconditioned heads from V8 developments, since then other than a noise that I've posted on here about before and seems to be somewhat common, it's been smooth and quiet.
Yesterday I did an oil change, as it is almost a year since the last one, despite only doing a couple of thousand miles since the last one. I hoped that fresh oil might have been all that way needed and the ticking would disappear, however unfortunately not.

Like most, I always have slipped liners in the back of my mind whenever I hear a noise that shouldn't be there. So to be sure, I did a quick coolant exhaust gases test with the coloured dye (was fine) and also checked all the spark plugs on the passenger side, but all were the same, no signs of water getting in. Plus when I had head gasket issues previously, I had coolant loss from over pressurising, a misfire and things, which I guess you'd expect if the issue was liner related.
At the moment other than the ticking noise everything seems to be okay, it runs fine and not using any coolant or oil.
Today I took the rocker cover off and then removed the rocker shaft, as I thought maybe it had a crack or damage, but I couldn't see anything wrong with it.

So I don't really know what to try next, the lifters were all new when I rebuilt it with the new camshaft, so I'd hope it wasn't a lifter, but I guess it could be. It could also still be the rocker arms or shaft too I guess. Worst case it could be a slipped liner, slapping up and down?

Here is a video of the noise, when warmed up, and with a gentle few revs - https://youtu.be/rVi6JLTqwg4?si=xwTyQqunoY5GN4s7

Any ideas what I should try next or anyone had similar?

Great, thanks Richard!

Looks like one to add to the list and probably change the thermostats too, so they get a bit warmer.

Looks like a few HEVAC tasks soon, as I need to sort my blend motors out too, as they've just started causing some trouble!

Actually... I've just answered my own question. So apparently I have heated seats that I didn't know about.

I don't have the correct HEVAC with seat buttons. Not sure if it was like that from new, the seats have been changed or if the HEVAC panel has been changed.

Weirdly when I bought it, the ad mentioned heated leather, but I completely forgot about it when I went to look at it and it was only a couple of weeks after I'd bought it I remembered this being in the advert.
Makes me suspect the HEVAC panel was swapped just before the sale.

I tested with the BECM output on the Nanocom and I can hear the relay click, but no heat. Testing with a multimeter, the connectors have 12V, but there is no continuity on the larger connector of both the left and right seat. The smaller connectors both have continuity, so looks like some of the elements are damaged.

Time to buy a HEVAC panel with the buttons and some new elements!