Hello Kev, I will try to reply in between lines:
the distributor can be quite easily taken apart and reassembled but make sure you don't loose any parts.You might also want to check you have the correct distributor as there are a number of different part numbers for the V8 with different advance curves depending on model/country etc. I don't understadn what you mean by the silicon wires in the distributor, if you mean the leads on the pickup, then you can do a check when you measure the pick up resistance. If you wiggle the wires with the dvm in place you'll soon see if there is a break in contact when the meter reading drops out but it doesn't sound like that's your problem because the engine would die same as turning the ignition off..
distributor was disassembled + checked and it is the correct model. The wires are those you describe, I thought they have silicon rubber insulation, but may be I am wrong. However, do you happen to know the ohm readings for the pickup? I will try and check this while bending the wires as if vac unit was at work and see if that occasionally cuts for a fraction of a second. This may not explain iffy idle as you call it, or problems with base idle setting, but could certainly explain why it cuts when accelerating, as vacuum unit will change timing. Will post the results of the test.
The ignition parts you say you have replaced - are they genuine Lucas parts?
You have said you have a new coil, is it a "high performance coil"? if it is bin it and put a standard one on it.
The ignition parts are not original Lucas but are good quality parts (sold by a known seller who got mentioned on this forum as well for quality - it's the place selling the red rotor arms etc you might have heard of)
I didn't know of high performance coils, mine is just standard ordinary replacement part (OEM) from a LR part provider
You say you have been turning the idle adjustment on the MAF
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What I also understand here is that you are saying you can set a base idle speed but the engine won't rev above 450rpm, this makes no sense to me because even if you disconnect the MAF and yank the throttle open it should rev. Or are you saying you can only set to a max of 450rpm using the adjustment screw in which case, you might need to tweek the actual throttle shaft, there is a small adjuster screw on the throttle linkage so you should be able to raise the idle speed.
There is no idle adjustement on the MAF as far as I know, I was talking about the setting screw on the plenum chamber, normally covered with a disposable piece of metal you remove by drilling + extracting. I would have thought the acting upon that screw might raise the RPM above the suggested value, hence the need to set it. In my case by unscrewing the setting screw it goes from nothing up to 450 and no more, to the point the screw is completely off and the engine dies for excess of unmetered air. Is the second throttle linkage adjuster screw you are mentioning the little one that can be accessed from below the plenum and is practically impossible to set when plenum chamber is fitted? I was reluctant to disassemble the plenum one more time.... but don't think I am lazy, it's just that I did it so many times I find it very boring now.....
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However, as per the workshop manual the throttle valve position is measured as the distance of upper and lower edges to the plenum chamber big bore on a vertical diameter, and this measurement should should give values differing not more than 0.5 mm. The reason why I never touched the small adjuster screw is that doing so would bring the above measurements out of specified limits. Should I do it, how far should I go to allow for some excess RPM in order to adjust base idle with the usual procedure? In other words, how much above upper RPM recommended limit should a complete unscrewing of the base idle setting screw allow? If I knew that I might try to set the small linkage adjuster to get to that value.
As for the last point, I also thought trying to swap ECU would be a good idea but unfortunately in my area this car is not very frequently found or serviced... (it's 27 yr old etc etc). Obviously that would be a critical starting point to make sure my chasing is not pointless.
I also thought of gas analyser to set that as a starting point, but if I had ignition problems, wouldn't that make my AFR look rich and be misleading?
Many thanks for your time. I appreciate very much the help and the attempts of exploring the issue. I tend to give all the details I have accumulated, hopefully this doesn't sound as if I pretend to know everything about it. It's just information that could be useful to solve the problem(s).
Ciao
Adri