Could be damp or HT leads breaking down. How old are they? Might be worth splashing out on a new set.
I bought and put on a new set but one or two kept coming off the spark plugs.... So I put the old ones back on. The new ones felt more pliable than the old ones which feel harder, thicker...but the look like there seen better days.
Worth while purchasing some decent quality ones Bosch etc. Don’t buy the poor quality lead sets, only fit for the bin.
How are they clipping on? You know not to use the screw on bits? The leads originally clipped onto the ‘threads’ on the plug. The screw on bits are for other types of leads. Then again...depends what kind of leads you have! They should be a snug fit and take a bit of effort to pull them off.
No... It used to run perfectly (as can be with a bus) So..I thought I'd 'renew' some well worn looking parts....HT leads, coil...'can only help' I thought. This lead to worse running, leafs jumping off, no power. So.. I replaced the old leads and better but has this problem. I've left the new coil on.
I cleaned up the rotor arm, swapped the distributor cap and changed the plugs (after 11k miles electrodes and insulators were nicely light brown, but the outsides of the plug insulators were dirty ) - removed juddering a couple of weeks ago. It was definitely a misfire - the AFR flickered lean as the engine juddered. Only noticeable in my case at high revs in first gear and pootling along at 30mph in 4th..
So you have an accuspark electronic module in the distributor? Do one change at a time, and always test to see if it's made a difference or not. Otherwise you'll tie yourself in knots. But, if you do have accuspark, make one of those changes a reversion back to points. At least it eliminates a dodgy electronic module. They are not always as fool proof as some may have you believe
Do you know if you have a module instead of.points? Lifting the top of the distributor cap and removing the rotor arm will show either conventional points, or a small black plastic box. @mikedjames has oodles of experience with changing these and could probably talk you through it? If necessary...