Q: Missing IAC valve vacuum line.

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I recently redone my vacuum lines and noticed a small port on my IAC valve that while open caused some hesitation in the engine but after capping it off the engine runs alot smoother, even during shifting gears. My vacuum lines seem to have a T-splitter near this area and I was wondering if this was an indication that the IAC was meant to have one of the lines from my Carbon filter box run to it instead of having it capped off.

My car has 187000 miles.
My car has a manual transmission.

The IAC (Idle Air Control) valve is required to have a vacuum line on it to work the engine properly. The line from the carbon box filter is supposed to be hooked to it, but it may be damaged. Take the hose on the carbon box filter and suck on it to see if it holds a vacuum. If it does, then I suggest hooking up the hose to the IAC. If it does not, then I recommend replacing the carbon box filter and then hooking up the vacuum hose to the IAC. If you need further assistance with your vacuum lines disconnected, then seek out a professional, such as one from Your Mechanic, to help you.

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