Q: Mass Air Flow replacement and problems with a fast idle

This may be related to a dirty or faulty idle air control valve. As you may know, this works similarly to the mass air flow sensor in that it relays air information to the computer which then makes adjustments to fuel based upon this information. The idle air control valve, however only operates at low speeds and at idle. This allows the proper air/fuel mixture to happen at idle and also when the engine rpm’s are decelerating from a higher rpm.

When this is not working properly, this may cause an erratic idle as you have described. This may also be caused potentially by an intake air leak or a vacuum leak as this will create a lean fuel condition also causing a higher idle speed.

To avoid any unnecessary repairs, I would recommend having an expert from YourMechanic come to your location to diagnose your high idle condition and service your idle air control valve as necessary.