Intermittent misfire

[C35Rob]

My 'misfire' issue seems to be back, drove a few miles no problem, gave it a few hard pulls and when it settled down to idle it was missing at idle and up to about 3k revs where it seems to clear..

Coil: removed, inspected, no cracks etc, measures out ok IAW bgb resistance specs
Leads: NGK leads, 1500 miles old, resistance between 3K and 6K (obviously less resistance on shorter leads)
Plugs: new NGK bcr8es, clean, gapped to 0.75mm
Dizzy cap and rotor arm - 1500 miles old, not China crap, clean and bright conductors.

Grounds are all good, connectors securely clipped in.

Let the car cool down and it goes away, didn't happen on the rollers, hasn't happened any time at all when I've been road mapping.. Totally intermittent.

I'm going to buy a new coil just in case it's breaking down under heat/load, probably get a new igniter too to rule it out.

Comments?
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[Martin F]

I had similar issues on an old outboard, turned out that the coil was producing a weaker spark when it started heating up...

p.s. I have a couple coils/ignitors in the shed, both worked fine on previous cars, you are welcome to borrow one if you cover postage and buy it if it works....

[C35Rob]

I'm going to buy a brand new coil for peace of mind, I wouldn't mind trying a different igniter though if you can send me one?

Cheers

[C35Rob]

Done about 60 miles in it this afternoon, some quite 'spirited' driving, no issues at all

[Martin F]

Done about 60 miles in it this afternoon, some quite 'spirited' driving, no issues at all

My money is on the coil, I remember reading posts in the past with exactly the same symptoms, coil was the most common culprit.
If you want me to post the ignitor pm me or if you would rather wait to see what happens when you replace the coil , That's fine also

[C35Rob]

Done about 60 miles in it this afternoon, some quite 'spirited' driving, no issues at all

My money is on the coil, I remember reading posts in the past with exactly the same symptoms, coil was the most common culprit.
If you want me to post the ignitor pm me or if you would rather wait to see what happens when you replace the coil , That's fine also

just ordered a brand new NGK coil, I'll wait and see how I get on with that and if it rears it's head again I'll grab an igniter off you

[oVerboost]

As your planning to do, replace the coil but also don't rule out a faulty component on the ignition side even if it appears to be okay, or even if recently changed. I had a faulty distributor cap in the past that caused endless issues yet at the time I ruled it out because it had only been fitted a few weeks before, yet it must have had an issue when manufactured. Fitted the old one back on, and the problem went away... So now I only replace parts when they need doing, not for peace of mind lol.