Check the integrity of all the vacuum lines and fittings. A cracked hose can result in unpredictable idling.
regards,
Phil
Well, I thought that this would be an easy lead, so I checked the lines and found one with a kink in it and corrected it by loosening a near tie wrap. Today I took the Morgan to work for a test drive and I could not reproduce the error. So perhaps... this did the trick.
Thanks for all the follow up!
Bert