The V8 Owners Forum -

Thank you so much.

The white plugs are a recent issue, having checked for air leaks and changed lambda's, idle control valve, ECU water temperature sensor, fuel pressure regulator (it was the regulator in my instance as soon as it was replaced the system held pressure whereas it wasnt before), fuel filter and checked for blockages am I right in saying the only thing remaining that could alter fueling is the MAF, TPS and the ECU itself?

I will return to the 123 distributor (it is new), I am going to try an MSD 6AL to avoid running without an amplifier.

The dial gauge has a 14mm adapter, I understand what you are saying due to the angle of the spark plug hole to the piston crown. I set the dial gauge so that it barely touched the piston I could turn the engine over and clearly see when it reached that position. Perhaps not truly accurate but I dont think its far out.

I am willing to try open loop but would still like to try and find out what has happened to create this issue.

Question about Crankcase breathing.

I have always been puzzled as to why RPI blocked off the rocker cover air intake filter with a blob of silicon - On the passenger side there is an outlet that feeds directly into the atmospheric side of the throttle butterfly from the rocker cover flame trap - Comparing this to the original Hotwire system there is an intake filter on the passenger side rocker cover, a flame trap on the drivers side that has a similar pipe leading to the outer side of the throttle butterfly and in addition a pipe leading to the plenum. In my case RPI put a blanking sleeve over the plenum intake. This is taken from the Hotwire training video - The Thor system from what I have read uses the pipe on the atmosphere side of the throttle butterfly as its intake, this goes to the passenger side rocker cover. The air goes through the crankcase and exits through the drivers side rocker and into the plenum.

So in both cases old and new they have an air intake and exit, I only seem to have the one connection.

No longer trust what RPI have done any opinions on what should be there?

This is a similar ACT Plenum set up and you can see the 'T' for the connection to the plenum, in another picture I can see the EFI style air intake filter - Makes me wonder if it was just too much work for RPI to add the T, it is quite tight space wise

heli_madken wrote: ↑Thu Oct 09, 2025 3:29 pm The white plugs are a recent issue, having checked for air leaks and changed lambda's, idle control valve, ECU water temperature sensor, fuel pressure regulator (it was the regulator in my instance as soon as it was replaced the system held pressure whereas it wasnt before), fuel filter and checked for blockages am I right in saying the only thing remaining that could alter fueling is the MAF, TPS and the ECU itself?

I must admit I'm not a big fan of simply changing parts to try and fix an issue, I much prefer to try and diagnose a situation and work out what the problem is. Changing parts can introduce new problem either because they are also faulty (even if new) or due to disturbing something else during the swap.
I'd much prefer to pick up as much data as I can and work out what the problem is.
For instance you seem convinced that you have a lean running issue but I don't see how this can happen on a closed loop setup without the trims showing this up. You say there was very little trim action in RG at idle so this doesn't seem to be occurring there, perhaps the system is running lean under certain conditions which is causing the plug colour so I'd be chasing a log from RG to see what happens in as many different conditions as possible.

Looking at the items you have mentioned I've put some thoughts below, but I'm not completely convinced you have an absolute positive result on your fuel pressure just yet, particularly as this is a very likely candidate for low power. Having the ECU open the injectors for longer won't supply any more fuel to the engine if not enough exists.

When I was looking at this on my own car a while back I initially piped up a physical pressure gauge so I could monitor fuel pressure. The problem is that this will move up and down as you load the engine. High pressure on closed throttle dropping 8-12PSI on WoT so you have to try and reconcile the readings.

MAF
This gives a signal which allows the system to find a row on the fuel map to extract a value from, if this is wrong then the system may add too much or little fuel but this will show up on the lambda readings causing a change in trim value. Again a log should help to see what is happening.

TPS
I'm not sure how much affect this will have but I don't think much. From the 14CUX code I've looked at the TPS is used in a few different ways.
1) Determining closed throttle. This will allow the system to drop into its idle mode. Obviously only affects specific conditions. Not likely causing your issue.

2) Wide open throttle (or at least very high). Not sure if 14CUX does anything about this but this would be a very specific condition anyhow and can probably be ignored.

3) Throttle direction (opening or closing) and rate of change. This will have an impact on fuelling particularly when the throttle is opening, this is to give an accelerator pump type of behaviour. This could have a bearing on your issue but it's hard to see how exactly. An RG log would help see if there are any sudden, non-viable changes in reading.

One other possibility could be an air leak between the MAF and the plenum which only occurs under some conditions. I'm thinking along the lines of a split hose which opens up when the engine moves under load then seal up again at idle.

heli_madken wrote: ↑Thu Oct 09, 2025 3:29 pm The dial gauge has a 14mm adapter, I understand what you are saying due to the angle of the spark plug hole to the piston crown. I set the dial gauge so that it barely touched the piston I could turn the engine over and clearly see when it reached that position. Perhaps not truly accurate but I dont think its far out.

I think I'll have to visit my dial gauge adaptor again. I made up a piston stop which gave me a decent reading and I kept adjusting it until it stopped just before TDC, 0.5mm shorter and the piston did not stop, so I know how long the DTI would need to protrude.

heli_madken wrote: ↑Thu Oct 09, 2025 3:29 pm I am willing to try open loop but would still like to try and find out what has happened to create this issue.

Possibly best to hold off on that for now, thinking about it you will only introduce more unknowns as your system is running a different MAF hence the calculations for load may not be the same.

Where about are you located BTW.

heli_madken wrote: ↑Thu Oct 09, 2025 4:06 pm Question about Crankcase breathing.

I have always been puzzled as to why RPI blocked off the rocker cover air intake filter with a blob of silicon -


On the passenger side there is an outlet that feeds directly into the atmospheric side of the throttle butterfly from the rocker cover flame trap -


Comparing this to the original Hotwire system there is an intake filter on the passenger side rocker cover, a flame trap on the drivers side that has a similar pipe leading to the outer side of the throttle butterfly and in addition a pipe leading to the plenum. In my case RPI put a blanking sleeve over the plenum intake. This is taken from the Hotwire training video -


The Thor system from what I have read uses the pipe on the atmosphere side of the throttle butterfly as its intake, this goes to the passenger side rocker cover. The air goes through the crankcase and exits through the drivers side rocker and into the plenum.

So in both cases old and new they have an air intake and exit, I only seem to have the one connection.

No longer trust what RPI have done any opinions on what should be there?

I must admit I've always been a bit confused by this system. Mine is setup as I believe you are describing with the small filter on the rear of the LH rocker cover (possibly including a metered orifice) which will be an inlet with gas extracted from the flame trap on the RH rocker cover. The pipe from the flame trap Tee's off to the plenum with a small bore tube (possibly with a controlled orifice inside) while a large bore tube goes to the throttle body area on the MAF side of the butterfly. This seems to give the possibility of unmetered air entering the engine.
Presumably this would only be an issue at low throttle openings when plenum pressure is low as is metered airflow. Obviously it must have worked as it was used without issue on many vehicles.


RPI really seem to have been up to some cowboy antics here throwing some very expensive parts together with some very questionable 'glue'.
Rather than considering reverting to carburettors as you mentioned in previous post how much work would it be to return to a standard 14CUX system, at least temporarily?

Ian Anderson wrote: ↑Fri Sep 26, 2025 6:32 pm Is it perhaps something simple as a bad earth/ground connection

You could be right!

I decided to strip out the engine loom as I have never been happy with what RPI supplied. During removal I found a group of earths tucked down out of sight at the back of the block which I have never noticed before. The bolt holding them on was hanging on just by a few threads I was able to remove it by hand - Not traced them through yet but I remember reading somewhere that they are important for engine running.

Have I found something significant do you think?

The latest misfire issue started after I had worked on the injectors I must have disturbed the earths in some way during disconnection/reconnection.

I would think so hence my check the earths comment a while back.

Could the plugs be too hot a grade ….I cannot see where you mentioned what you had fitted. I seem to remember BPR6ES plugs.

But memory fades

Ian

Thanks Ian,

Unwrapping the loom both Lambda sensors earth through the point I have found so that isnt going to help.

The car came originally fitted with BCP6ES supplied by RPI which isnt correct (non resistive) so I fitted BCP6RES these where ok originally but started turning white when I started experiencing problems. I spoke to Mik Pierce from NGK uk and he felt that I should try BCPR6EIX Iridium plugs which also burnt white. I have just reviewed his answer and he does go on to say that I could also try BCPR7EIX, which are colder, if the engine has been heavily modified, perhaps this is the way forward.

heli_madken wrote: ↑Sun Oct 12, 2025 4:30 pm Thanks Ian,

Unwrapping the loom both Lambda sensors earth through the point I have found so that isnt going to help.

The car came originally fitted with BCP6ES supplied by RPI which isnt correct (non resistive) so I fitted BCP6RES these where ok originally but started turning white when I started experiencing problems. I spoke to Mik Pierce from NGK uk and he felt that I should try BCPR6EIX Iridium plugs which also burnt white. I have just reviewed his answer and he does go on to say that I could also try BCPR7EIX, which are colder, if the engine has been heavily modified, perhaps this is the way forward.

I thought the standard plugs for the rover were BP6ES, don't know what the "C" means.
In any case I can't help thinking you are overthinking this and throwing parts at it. Iridium plugs will last longer than standard but they aren't going to work any better. Some people who should know better than me tell me they don't work as well.
Personally I'd be checking the basics, like your wiring, before throwing any more parts at it. Doing that just makes it like trying to hit a moving target.
Have you tested the car since you sorted out those grounds? If so any better?

I will hold off on the new plugs for the time being. I dont know what the C stands for either but in an EFI engine they should at least be resistor type plugs. When I bought the BCP6RES I think I still tried to believe RPI knew what they where doing installing BCP6ES but in truth I have since realised they have just put on my engine whatever they had lying around. I think, unfortuantely for me, mine was one of the last engines to be built before ceasing to trade.

I havent tried the engine since finding the earth issue, I am doing what I should have done in the first place stripping all the loom tape off the engine loom and have a good look for any issues.

This is the sort of thing I am finding, all done by the same person as they didnt have any insulating tape handy or a soldering iron so either left connections bare or wrapped with loom tape and wires just wrapped together - This is the ECU water temperature sensor cant imagine it was working with the correct values at all. Not sure why you would replace a faulty plug then make a pigs ear of connecting it.

Going to check every last wire for continuity and re-wrap.

Hi Heli

First of all, apologies if I came over a bit short in my last post, I developed a stinking cold over the weekend and that coupled with lack of sleep has taken me out of my normal, good natured, comfort zone!

Having said that though, what really does upset me is seeing people being taken for a ride and I really do think this is what RPi have done with you. Based on the kit which has been assembled on your engine I'm assuming (better than that, I "know") a significant amount of money has changed hands and you really do deserve to get what you paid for. I just hope the internals of your engine are in better shape than the peripherals.

heli_madken wrote: ↑Mon Oct 13, 2025 12:19 pm I dont know what the C stands for either but in an EFI engine they should at least be resistor type plugs.

I dare say that the BCP6ES plugs are only slightly different than BP6ES so I wouldn't worry about that at the moment.
In fact I just did a bit of a search and found that the difference between B & BC is the hexagon size 25.4 vs 16mm so should not make any difference to the function of the plug but I agree that is should be a B(C)PR6ES rather than the B(C)P6ES although I don't think that would contribute to your issue.

heli_madken wrote: ↑Mon Oct 13, 2025 12:19 pm When I bought the BCP6RES I think I still tried to believe RPI knew what they where doing installing BCP6ES but in truth I have since realised they have just put on my engine whatever they had lying around. I think, unfortuantely for me, mine was one of the last engines to be built before ceasing to trade.

I think from the point of view of sorting out your issues you're probably best ignoring what has gone before and working forward, don't make any assumptions about who put the kit together and just check everything.

I think physically checking all the constituent parts are physically correct, as you are doing with your loom, is a good way of looking at it and I also think testing such as via Rovergauge a positive step as it will allow you to diagnose the problem(s).

heli_madken wrote: ↑Mon Oct 13, 2025 12:19 pm This is the sort of thing I am finding, all done by the same person as they didnt have any insulating tape handy or a soldering iron so either left connections bare or wrapped with loom tape and wires just wrapped together -
20251013_125726.jpg

This is the ECU water temperature sensor cant imagine it was working with the correct values at all. Not sure why you would replace a faulty plug then make a pigs ear of connecting it.

Going to check every last wire for continuity and re-wrap.

That is absolutely horrific, complete disgrace! I always try and look for the positive so what I'd take away from this is that even if that is not what is causing your problem now it would be doing in the future so good to find and sort early on.
The fact that this is your temperature sensor could contribute to your issues as an incorrect reading would lead to incorrect fuelling. Only thing I would say is that if the temp' reading was low the result would be adding fuel, running rich rather than lean.

Completely checking that loom is the only way to go.

Keep at it, I'm sure there will be more horrors to find.

No Problem, very glad for your help.

Yes I did pay a frightening amount of money for what was supposed to be a 'Plug and Play' engine requiring only basic electrics, fuel, cooling and timing etc. I did a lot of research into RPI and at the time saw mixed reviews. My decision to use them was the plug and play element which no one else seemed to offer. At the time I knew nothing about the 14CUX system so did not feel confident enough to put a complete system together although I could now.

The first thing that went wrong was communication, as soon as I had paid for the engine trying to contact them was extremely difficult and there was a time that I thought I wasnt going to take delivery.

The first inclination that things where not going to go smoothly was the main harness connection. This did not match my car so it took some investigative work on my part to work out which wire went where. From then on things just got worse, the loom as mentioned before had been butchered and it was only after unwrapping parts of it that I found the faults.

Since then I have had multiple peripheral failures starting with the alternator.

Even trying to inform DVLA of the new engine was difficult as I missed the fact that the receipt for the engine did not include cubic capacity or serial number.

The whole thing has been a nightmare, that said I do think the core of the engine itself is ok. I get the impression that this was built with care but then everything else was done shoddily by another individual.

I keep looking at the itemised bill and the premium I paid for everything which depresses me, I should really throw it away.

My wife did manage to track the owner of RPI down, he now lives in Thailand. I wrote to him and to be fair he was helpful to an extent but no notion of an apology for the problems and failures. I have tried to be 'nice' to him but once I get everything sorted, well I already have the email composed in my head.

Pressing on with the wiring loom, I have found several more issues to fix, just working my way through everything.