Interesting ignition problem

Ok I was on a freeway travelling 60 mph for 20 miles all good car has been performing beautifully for last 800 miles after initial 100 mile sort out…… get to end of freeway and starts missing …… so limp it home …. Changed plugs, new coil, checked dash pots and fuel bowl for water …… not a change in the motor … checked voltages and spark…… some how not firing on different cyls …not consistent…… turns out that electronic ignition is not set and forget…… the Hall effect magnets and module have an air gap…… mine had somehow changed although nothing was loose …. adjusted the air gap (mechanic did) …. Back to as good as gold…… so I learned something new! Mechanic thinks that it was probably not installed correctly and been “ on the edge” all along but that with heat the magnets loose some of their power over time and that meant that the air gap was just too big ….interesting!

I run all my cars with points. Every couple of 1000 miles I replace them.

My cars start, and run fine. Just sayin’.


It’s not like I don’t have plenty of points I do probably 100 sets …. But I was being lazy I guess…. Mind you I do have a set of points sitting on a plate in the boot!

One of my cars with Pertronix module developed a strange miss sometimes. Turned out the pivot point for the vacuum advance plate wore and could allow the air gap between the magnet and module to change. It is now one thing I check occasionally on my cars with Pertronix.

68 E-type FHC

The quality of points must really have gone downhill!

Back in the dark ages, when p&c were of good quality , I’d readjust every 2000-3000 miles, but had no need to replace them until 10-15,000 miles of use.

I’m glad they are mostly dead.

I have the genuine Lucas points nos

Ah ha …. Mine is Petronix as well ….I too will now be keeping an eye on it closely

If so, and they need replacement every couple 1000 miles, something is terribly wrong.

I don’t use points …… just saying that I have them…… andrewbowie is the one that changes his …… I’ve always found Lucas points to be fine on my other old cars … more like you say occassional adjustment is needed every 2000 miles

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Mine get replaced when I do a big service on my cars.

As I currently have 3 E types and a Mk2 with points this works out to be every couple of years. But I rarely exceed 1000 mikes in that time, per car.

It’s probably unnecessary but it’s just as easy to replace them as adjust them, so I do.

This is an older thread but here is a follow up …after about 300 miles it started to do it again……. So I knew it was the “ air gap” issue!..…. Opened up the dizzy….and could see some crud in the air gap……took the rotor ring off…… and found there to be a piece of spring metal from a rotor attached to the ring ….looked at the rotor ….not from this one …… I do remember at one stage having a rotor smash up as the cap was not on correctly …must have left that pesky bit of metal in there…… removing the offending metal and refitting everything …. And purrrrr😃 done another 350 miles no issues …I think I’ve fixed it permanently this time.