Administrator, Resident Tater Salad
Background: manifold and everything attached to it was replaced recently for PCV issue. I think it comes with the throttle body, EVAP valve, and possibly injectors.
Since then, completely randomly, I've had a bit of a stumble on startup - either first thing in the morning or sometimes after a hot soak. 90% of the time, it'll crank over and fire up normally. Yesterday was particularly bad - it stumbled to life and then RPM hunted around 1500 up and down for 5 seconds or so. Then it acted like nothing happened and the idle settled down to 1000 after 15 seconds.
Car runs great otherwise, and no noises or anything else to indicate a vacuum leak. I checked the throttle body (new) for oil buildup, checked for vacuum leaks at the intake manifold to head ports (nothing), and then checked the coil pack/plugs. Nothing wrong with anything there.
The more I think about it, the more I think it's the purge valve or the check valve right after it (also new). Hot starts and near full tanks of gas seem to really be the only correlation to getting the stumble regularly - it has happened on cold startups after sitting for a number of days only 2-3x.