System and method for controlling an operating frequency of a purge valve to improve fuel distribution to cylinders of an engine

1. A system comprising:

an engine speed module that determines a speed of an engine based on a position of a crankshaft; and

a valve control module that selectively adjusts an operating frequency of a purge valve to a first frequency when the engine speed corresponds to a harmonic of the operating frequency of the purge valve, wherein the engine speed does not correspond to a harmonic of the first frequency.

2. The system of claim 1 further comprising a harmonic speed module that determines a first speed of the engine that corresponds to the harmonic of the operating frequency of the purge valve, wherein the valve control module adjusts the operating frequency of the purge valve when the engine speed is equal to the first speed.

3. The system of claim 2 wherein the valve control module adjusts the operating frequency of the purge valve when the engine speed is within a predetermined range of the first speed.

4. The system of claim 3 wherein the valve control module decreases the operating frequency of the purge valve by a predetermined amount when the engine speed is within the predetermined range of the first speed.

5. The system of claim 3 wherein the valve control module maintains the operating frequency of the purge valve at a predetermined frequency when the engine speed is outside of the predetermined range of the first speed.

6. The system of claim 1 wherein the valve control module:

adjusts the operating frequency of the purge valve to the first frequency when a frequency corresponding to the engine speed is within a predetermined range of the harmonic of the operating frequency of the purge valve; and

selects the first frequency such that the frequency corresponding to the engine speed is outside of a predetermined range of harmonics of the operating frequency of the purge valve when the operating frequency is adjusted to the first frequency.

7. The system of claim 1 further comprising a converter module that converts the engine speed into a frequency of the engine, wherein the valve control module adjusts the operating frequency of the purge valve when the frequency of the engine is within a predetermined range of a harmonic of the operating frequency of the purge valve.

8. The system of claim 1 further comprising a valve harmonic module that determines harmonics of the operating frequency of the purge valve, wherein the valve control module adjusts the operating frequency of the purge valve when a frequency corresponding to the engine speed is within a predetermined range of one of the harmonics.

9. The system of claim 1 wherein the valve control module selectively adjusts the operating frequency of the purge valve further based on a duty cycle of the purge valve.

10. The system of claim 9 wherein the valve control module selectively adjusts the operating frequency of the purge valve based on the engine speed when the duty cycle of the purge valve is less than a predetermined percentage.

11. A method comprising:

determining a speed of an engine based on a position of a crankshaft; and

selectively adjusting an operating frequency of a purge valve to a first frequency when the engine speed corresponds to a harmonic of the operating frequency of the purge valve, wherein the engine speed does not correspond to a harmonic of the first frequency.

12. The method of claim 11 further comprising:

determining a first speed of the engine that corresponds to the harmonic of the operating frequency of the purge valve; and

adjusting the operating frequency of the purge valve when the engine speed is equal to the first speed.

13. The method of claim 12 further comprising adjusting the operating frequency of the purge valve when the engine speed is within a predetermined range of the first speed.

14. The method of claim 13 further comprising decreasing the operating frequency of the purge valve by a predetermined amount when the engine speed is within the predetermined range of the first speed.

15. The method of claim 13 further comprising maintaining the operating frequency of the purge valve at a predetermined frequency when the engine speed is outside of the predetermined range of the first speed.

16. The method of claim 11 further comprising:

adjusting the operating frequency of the purge valve to the first frequency when a frequency corresponding to the engine speed is within a predetermined range of the harmonic of the operating frequency of the purge valve; and

selecting the first frequency such that the frequency corresponding to the engine speed is outside of a predetermined range of harmonics of the operating frequency of the purge valve when the operating frequency is adjusted to the first frequency.

17. The method of claim 11 further comprising:

converting the engine speed into a frequency of the engine; and

adjusting the operating frequency of the purge valve when the frequency of the engine is within a predetermined range of a harmonic of the operating frequency of the purge valve.

18. The method of claim 11 further comprising:

determining harmonics of the operating frequency of the purge valve; and

adjusting the operating frequency of the purge valve when a frequency corresponding to the engine speed is within a predetermined range of one of the harmonics.

19. The method of claim 11 further comprising selectively adjusting the operating frequency of the purge valve further based on a duty cycle of the purge valve.

20. The method of claim 19 further comprising selectively adjusting the operating frequency of the purge valve based on the engine speed when the duty cycle of the purge valve is less than a predetermined percentage.

21. The system of claim 1 wherein the harmonic of the operating frequency of the purge valve includes a frequency other than the operating frequency.

22. The method of claim 11 wherein the harmonic of the operating frequency of the purge valve includes a frequency other than the operating frequency.