About a week ago, noticed some rough idling on my 1988 B2200 5-speed with Weber carb, felt like a vacuum leak, my tachometer needle was jumping, didn't seem different once rpm were up as I was driving. Today I had time to check the oil, noticed this rubber vacuum cap just sitting on the top of the manifold.

So I then looked for an open port on the intake manifold, found this


The rubber cap fit loosely, so I used a short piece of vacuum tubing and a cut-off wooden golf tee to fix. All done !!!

 

Cusser, you can also "link" two unused vacuum ports together, with a short piece of vacuum hose connected between them......no need to use a golf tee then!

 

Yep, used to do that when I had to pass emissions tests. The "techs" didn't like capped-off vacuum ports once the stock air cleaner was removed for the Weber and were visible, so linked some together to make the "techs" think they were doing their job conscientiously. "Techs" didn't have equipment to test integrity of the fuel vapors on my 1971 VW, so they "tested" my all-metal gas cap for leaks.

 

What's weird is that a few weeks ago when I noticed the poor idle, I removed both idle jets on the Weber 32/36 DGEV and made sure they weren't clogged. So apparently I missed the vacuum cap that had come off and the manifold port uncapped just a few inches away from the secondary idle jet. Maybe that was because I do put down a towel in case I drop the jet or O-ring.....

Just shows that it never hurts to double-check, or take a second look !!!!