May 17, 200816 yr Author comment_247772 One thing that will cause a stumble when coming off idle is if you are using ATF or similar thin oil in the carbs . This causes a lean mixture just coming off idle. Switch to 20wt and this will eliminate this . You may have other things going on but this will help a lot. ATF is 5wt too thin. The light oil causes the vacuum piston of the dampener to rise quickly. This is the opposite of what the dampener is designed to do. GaryAgreed. I only use 20wt. Link to comment https://www.classiczcars.com/forums/topic/28087-hard-starting-when-cold/?&page=2#findComment-247772 Share on other sites More sharing options...
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