CIS Surging when damp/wet conditions
 

Hi all, hope someone can help.
I have a 1980 911 SC, that has a problem with surging revs when it rains or in very damp conditions.
Runs fine all other times.
All the vac pipes have been checked and its also been checked for air leaks.
Where would a good place to start be?
Thanks.

Distributor cap for moisture when it rains.
How old are the plug wires?
Are they Covered in metal sheathing? Search for light show at night!


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Next time it happens nudge the mixture screw toward lean. Humid warm air changes the AFR enough that a setting on the rich side can begin to oscillate at idle. If that's not it nudge it back where it was.