Can Evap system cause intermittent vacuum leak? | Ford Explorer - Ford Ranger Forums - Serious Explorations

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Can Evap system cause intermittent vacuum leak?


Well-Known Member
October 29, 2012
Reaction score
City, State
Colorado Springs, CO
Year, Model & Trim Level
2005 Lincoln Aviator
Looks like maybe I have a vacuum leak that only occurs when engine RPM's drop down or shortly after vehicle stops. This is based on scan data. I disconnected the IAC plug and found that my actual RPM is often higher than desired RPM. (Actual 700-750 desired 624). This would indicate a vacuum leak. This looks like it is confusing the PCM and causing incorrect IAC commands.

This engine is tight as a drum. I've verified all the normal static vacuum leak causes. So I'm down to the Evap system, or possibly the PCV. Thinking about temporarily disconnecting both and plugging them and see what happens to the idle speed.

Anyone ever have either system go bad and not throw any codes? Seems really odd that I could have enough of a leak and not have a code.