Thanks for clarifying you’ve potentially saved me some money there! I will just have to gather some more data by driving it as much as possible in the sunshine, poor me! Heard of a cooling temp sensor causing misfires before?
I had this issue on a mk2 I bought last year .
The oil from the cam cover leak was tracking down the wire of the crank position sensor .
The oil on the sensor caused the misfire .
Check the wire for oil , clean the crank pos’ sensor and ensure proper size gap from pulley
Cheap fix if it’s this 
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Great tip mate thanks I’ll get right on that, it’s definitely a bit greasy back there.
My coilpack and leads were greasy with oil from my old valve cover gasket issue. I cleaned them up and changed the coil pack for a new one a couple of days ago, it’s been running well since! Fingers crossed that’s it sorted. Attached a photo of my old coilpack, I didn’t test it but one of the contact wells was black as you can see. I expect this may have been causing the issue in conjunction with oily leads. Thanks again for all your advice, really great.
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Nice one, I think you have nailed it. A connection problem rather than a coilpack failure per se.
It is possible to clean that corrosion out of the port. I use a dremmel and then soak in lemon juice:-)
The HT lead is probably toast though.
Worth having a go at the coil unit, just to see if it is of any use as a spare.
Quite common on the MK2, particularly 1.6 for water to get drawn into a high tension port on these coil units. Usually only one effected. I think it must be temperature change causing a vacuum so any ambient moisture sucked in under certain circumstances. Just check those ports every so often, perhaps when servicing.
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It happens on other cars too.
Years ago I saw where the oil had wicked up the wire-core lead from the plug well and into the distributor cap, softened the “hard” plastic enough to cause erosive arcing and a small hole and then dripped down onto the points!
A friend brought it into work because he could not believe it had happened.
We all went out and had a look at the exotic old thing (Maserati? Fractured memory from 30+ years ago). One of the others then mentioned his Stag where the leads fall off the plugs, but can also collect oil and/or water from above and have the same wicking effect inside the lead even if not the distributor erosion.
I found this excellent pic of a Stag engine (by EJWard) on the web
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I am largely immune because my car is in the garage…but the other halves, sits outside in the South Devon elements 24/7.
I like to understand why such things happen, especially with degradation and corrosion. Quite fascinating how much of this is linked, almost like some sort of sympathetic, trace electrical lymphatic system running through the car. .
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My wife’s Panda had moisture wicking up a wire from the ecu multi-connector and causing corrosion.
It’s amazing what weird stuff can happen.
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I once moved into an MOD owned house already fitted with a TV aerial. I connected my telly to it and not long afterwards it started playing up in bad weather. One day it began making a buzzing noise before failing altogether. I then noticed water dripping out of the aerial socket! Whoever had installed the aerial had draped the cable down across part of the roof, instead of under the nearest tiles. The wind had blown the cable to and fro across the tiles until the outer insulation had worn away. Then rain water found the quickest way off the roof!
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This is about the only beneficial use I can think of for the original WD40, it is an excellent water repellent and the film self-heals. It kept our mini going for many years with the ignition system at the front exposed to the worst of the weather.
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Indeed.
WD supposedly stands for water dispersant.
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That is what it was designed for in USA,WD40 is the 40th blend of water Dispersant tested
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Ha, ha, I wonder how well WD41 would sell in comparison 
GT86 might do OK but GT87?
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