Intermittent misfire

[12jslater]

I've already tried two different could unfortunately, I have tried a known good coil, and a spare I had for a previous car.

[Austin Nippy]

Hi,
This is a real long shot but I had problems with my Nippy about 18 months ago where it ran well at times interspersed with being really rough / no real power / popping and banging at times / sometimes not wanting to start and so on. It turned out that most of the lip on the distributor base plate had fallen off so that the cap could move around even though it was held on by the clips. The effect was "variable" timing as the cap was free to move around on the base plate. Once I found this, it was a very quick and easy repair although it had me scratching my head a lot for a day or two before I found it.
May be it's worth a quick look to at least eliminate this from your search?
Best wishes,
Nick

[flywheel1935]

Many years ago had a similar issue, one night went into the garage, fired up, turned off all the lights and a big blue spark was flashing from the top of the coil to the firewall, crack in the coil top near HT lead ????

[12jslater]

IT'S FIXED


After lots of thinking, lots of cups of tea and LOTS of swearing it's done! I don't have a CLUE as what it was as I all I did is have the distributor out and checking everything once more, everything seemed absolutely spot on, refitted it and it's running without a misfire, I'm completely baffled.

I did absolutely nothing to it.

Ah well that saves me further swearing and wasting precious tea haha

Thank you to everyone for your suggestions!!

[Ivor Hawkins]

Hurrah! I’d like to say mystery solved, but at least you have got a result.

[John Mason]

When you took the dizzy out did you disconnect the low tension lead. If you did I bet it was a intermittent short or open circuit or possible poor conception to the condenser which was put right when the re connection was made.
I am pleased however the problem is solved and if it does re occurs you will know where to look.

John Mason.

[12jslater]

I never even disconnected the Lt lead, I just had a poke around the distributor while it was resting on the battery box under the bonnet, haven't a clue why it was

[David Witton]

Dodgy earth on distributor?