I have a 73' 350SL (3.5 gray market) that has always surged at idle cold, then smooth warm. Aux. air valve is functioning creating high idle, then it lopes or surges like its lean. Checked coolant sensor - ok. Don't know what else it can be. Help
I had the same issue with my 4.5. I replaced all the vacuum lines and solved the issue... Those plastic lines are available at a local parts store. If you go down this route, be sure to replace the rubber connector bits as well. They often crack with age.
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