AK260

Spot on! [emoji106] Also try it on the coil to dizzy cap cable - which is where the majority of my issues lay. It looks like your engine earth strap is next to your oil dipstick. Thick black wire goes from block to body. Your coil has positive and negative low tension connectors. One is 12v from your ignition switch and the other is the 0v that the dizzy breaks / makes as it operates. Also you have low tension connectors at your distributor - look at those too. These connectors tend to corrode. Especially in the UK where we are constantly humid. IMHO plug fouling at idle is a red herring here and given your photos they look OK. I had an L series that drank a lot of oil and the plugs were not just sooty but also wet and black - it never backfired or missed when cruising or on power. So your plugs for the sake of trouble shooting this issue look fine.

The way I looked at mine was v simple: eliminate every possible electric cause. I changed: the plugs in case one had a crack The dizzy cap and rotor The coil The wires to the coil by running direct from battery (fused of course) temporarily. Spark plug leads. Also Checked and cleaned up engine earth strap Replaced a couple of connectors - see this one that was holding by a single strand you can see coming out of the connector. Did each one at a time until I found the culprit - and I would say there were two issues in the HT leads and a potential other in the low tension connectors. Bear in mind I had rough running and backfire at revs and when on power and missing visible on timing light. So given my experience I would say your problem is electrical in nature not advance related. Good luck buddy.

Not sure if you fixed this issue but I had exactly the same problem - turns out my magnecore kv85 leads were the culprit. I had assumed being advertised as high end items they wouldn't break down after just 9k miles but the coil end had disintegrated and 2 out of 6 leads would change impedance dramatically - from around 5k ohms to over 300kohms - when you waggle them. The guy on the phone at magnecore was condescending when I raised it with him and refused to believe their leads could possibly fail. It's all the customer's fault ! Changed them for 8mm leads costing 1/6 the price and the car runs sweet as a nut again. https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F181999641503 Check / change your leads too and see what happens.