Engine Stuttering and hesitant

[William2]

I took my Elan S4 (Dellorto carbs) out for a decent run today and after about 20 miles of mixed town and country driving the engine started hesitating and misfiring/stuttering whenever I accelerated. I may be wrong but it seemed to happen when the engine gets hotter but I can't be sure it's heat related. Temp gauge reading 90 degrees C.The tick over was always fine and steady and sometimes it would clear itself and accelerate ok. When driving at steady speeds the engine seemed fine. Having covered about 2000 miles in the car over 3 years it usually runs without any issues or flat spots when accelerating. Might it be a spark plug causing it or is it carb/fuel related. Any comments/advice gratefully received.

[englishmaninwales]

How old is the coil? If old, it’s performance can drop off when they get hot. Is hot starting a problem, as this can be a symptom of a failing coil?
Malcolm

[ericbushby]

I think it would be worth replacing the spark plugs and rotor arm first. These parts are cheap and are known to cause the symptoms you describe. I have just this week changed a plug for the same fault.
Eric in Burnley
1967 S3SE DHC

[andyelan]

I'd say it's most likely the coil as from what you describe it seems to be affecting all cylinders. I personally don't think much of new coils sold today

The under bonnet temperature will be causing the coil to brake down and this will show up when accelerating, or otherwise loading up the engine, as this is when it's hardest for the ignition to fire the plugs.

As a check, if this happens again, stop and open the bonnet for about 10 minutes to let things cool down. When you set off again things should be fine for a while until the heat builds up then the misfiring will start again

[William2]

I have a Powermax electronic ignition fitted and a coil that is about 5 years old and made in China probably. I have just found in my garage a genuine NOS UK Lucas coil so I will fit that first. If the problem comes back I will replace the spark plugs. The plugs I am using are NGK BP6ES which I believe are correct for the car.

[Mike+2]

If the stuttering or surging happens while accelerating, or driving up hills.. I'd put money on fuel filter.

[William2]

It turns out that the electronic ignition module was faulty. Fitted a replacement and all working well again.

[ericbushby]

Hi William2
Sorted then, thanks for the update.
Eric in Burnley