Slight judder on long run

[Pete 21]

Hi- just done longest drive in my 35 years of owning my stag due to house move- c.120 miles of which 90 odd was motorway.
Generally I was pleased with how the car ran, temperature stayed constant even after coming to a traffic halt after motorway runs.
However, I did experience a ‘power judder’ two or three times when moving off from stationary in traffic- that sort of felt like ignition cutting momentarily.
I recently fitted a resin filled coil and moved to the bulkhead, as I was concerned it might overheat on the journey. I have electronic ignition (accuspark if I remember correctly).

Ultimately all was good as it quickly recovered each time , just a bit worrying to have sudden intermittent power drops 80 miles from home.

Any thoughts on cause please?

[MandM]

I had a problem like when I put my foot down it would miss fire, it was the rota arm on mine, I had only just fitted it, looked OK but was tracking under load

[NeilR]

Suspect accuspark/powerspark, those don't like getting hot.
Not much cooling air around the dizzy when stationary.

[Pete 21]

Thanks guys. Anyone else had issues with electronic ignition when running hot and is there a more resilient type (not points!) or means to mitigate.

[NeilR]

Yes, I had two of those units fail. Started with occasional misfire & just got worse over a few days.

Fitted a Pertronix, didn't fail and was on until I went distributorless wasted spark & EFI.

[Wheelz]

Hi- just done longest drive in my 35 years of owning my stag due to house move- c.120 miles of which 90 odd was motorway.
Generally I was pleased with how the car ran, temperature stayed constant even after coming to a traffic halt after motorway runs.
However, I did experience a ‘power judder’ two or three times when moving off from stationary in traffic- that sort of felt like ignition cutting momentarily.
I recently fitted a resin filled coil and moved to the bulkhead, as I was concerned it might overheat on the journey. I have electronic ignition (accuspark if I remember correctly).

Ultimately all was good as it quickly recovered each time , just a bit worrying to have sudden intermittent power drops 80 miles from home.

Any thoughts on cause please?

I've had a lot of experience of the generic Accuspark/Powerspark/Ultraspark electronic ignitions. The failure mechanism tends to be of the infant mortality type, but once you get a unit that works beyond that (perhaps up to 24 hours of running) I found that they usually work well over a long period of time. The brand doesn't seem to matter, as they all behave much the same, leading me to believe what I have heard, that they are all of the same design and source regardless of brand.

Cases like this suggest a weak spark, which might be rotor arm or cap, but before you blame the ignition module, check that you are not running a 12 volt coil on a ballasted circuit as this could cause a misfire. Also the ballast in the wiring loom can become intermittent causing misfires or complete cut outs.

[Pete 21]

Thanks Chris. As I say, I have recently fitted a resin filled coil (viper) due to concerns that performance would deteriorate with sustained heat on a longer run. I went for the 12v model as I understood this is what the electronic ignition needed and have served from a direct 12v feed. Ignition model, rotor arm and cap have all been in for less than 1k miles.

[Tdafforn]

I’ve put these hall effect type ignitions in all my classics for years. Only had one fail and that was when i shorted it out by mistake… oops.
tim