Engine miss when hot

[John Alves]

take a direct wire from your battery to the ignition system, and see if your problem is over, maybe you have an bad ignition switch with bad contact.

Also check your earth strap from body to gearbox.

Maybe run an separate earth from the battery as well, just to make sure.

Herman

Did all that a while back

[Tony Z]

back to basics.... when it starts happening, touch your coil. If you can hold it for 30 seconds, coil is likely OK, if its too hot to hold, coil is likely faulty.
It happened to me in the past and it was the coil. You could try changing it (yes, again).
Maybe consider changing dizzy, coil and whole ignition system from a car that is known to work. If it now works, you know it isnt electrical and its related to something in the mix that you removed.
Have you tried new plug wires? Old wires insulation becomes less effective when they get warm, and causes misfires.

[John Alves]

Have you tried new plug wires? Old wires insulation becomes less effective when they get warm, and causes misfires.

I replaced the whole ignition system from a car that is in working order, will touch the coil as suggested

[John Alves]

Coil is not hot Tony
I drove the car with the occasional miss with the hope that it would totally fail and then I could track down the
problem for good, well it finally happened (luckily outside my house) no spark to all 4 plugs, however there was 12v power to
coil. I replaced coil lead to dizzy and she started first time and purred like a kitten, went for a long drive with no
misses at all, I then put back the old coil lead as an experiment and all is still fine, I have been driving with the old
coil lead with no issues (I carry the new lead just in case) This does not make sense???

[Tony Z]

electrical and electronic issues sometimes make no sense.
We've had issues with the electronics on our CAT 3512's for over a year. We've had the CAT electronic guys onboard 4 times at a cost of around $15000 without any result. I stared at the drawings for about 6 hours before I thought I'd try something - swapped out a $20 relay and the issue is gone... sometimes things just dont make sense and you have to replace stuff until you find it. And sometimes you just need to start from the beginning again with a blank sheet and an open mind, like I did.

[Riaan.N]

Intermittent problems are the most difficult to find.

The plug wire you replaced, could it just have been loose or broken?

[73type2]

with a blank sheet and an open mind...

For me it's sometimes a blank mind and a full sheet!

[John Alves]

The plug wire you replaced, could it just have been loose or broken?

looked perfect to me

[Dawie]

Next move may be to, as a test, replace your Pertronics with original points distributor?

[retrovan]

Dawie has the right advice at the bottom of his posts..;-

Don't assume anything- (While doing fault-finding).

The only way to find a fault like that is to make a list of possibility.

And disregard what you have done before.

And do only ONE change at a time.

If it has no improvement put it back and try the next thing.

Go down the sheet in this way till you find it.

Do not skip a line, thinking it can not be or I have done it before, that will just prolong your toil

Do it to the book, and you will get it.

Herman

[retrovan]

I replaced coil lead to dizzy and she started first time and purred like a kitten, went for a long drive with no
misses at all, I then put back the old coil lead as an experiment and all is still fine, I have been driving with the old
coil lead with no issues (I carry the new lead just in case) This does not make sense???

It will depend how the lead is laid down, as it may have a pin hole that now is in air and can not discharge the spark, forcing it to the spark plug.

You can test it by fitting the old lead and when the engine is running, move your hand over the wire from front to back. if you get a shock, you know you found your problem.

Why not replace the spark plug cables and get done with it. ?

Herman

[John Alves]

Why not replace the spark plug cables and get done with it. ?

Herman

Yep, that is what I will do