How do I fix it

hot or cold engine High and how high is RPM not told.
no it is not evap failing to cause RPM failures.
2 problems sure, but not THE problem
well gas cap loose or bad is first. simple fix that is
costs nothing, and cap good or cap bad $10 fix.but not RPM off.
then purge solenoid.
RPM high is the best clue here. for sure
mine fails every 50k miles it seems and pull the valve
and flex the valve inside while spraying silicon oil spray inside it
and it goes 50k more miles costing me 50 cents lube.
497
Evaporative Emission (EVAP) System No Flow During Purge

the test in the service manual are extensive
example

• A loose, missing, or damaged fuel fill cap can cause this DTC to set.
• A stuck closed, blocked, or restricted EVAP canister purge solenoid valve, can cause this DTC to set.
• A blockage or restriction in the EVAP canister purge solenoid valve vacuum supply hose, EVAP canister purge solenoid valve purge pipe, EVAP canister, or vapor pipe, can cause this DTC to set.
• A temporary blockage in the EVAP canister purge solenoid valve, purge pipe or EVAP canister could cause an intermittent condition. Inspect and repair any restriction in the EVAP system.
• To help locate intermittent leaks, use the J 41413-200 Evaporative Emissions System Tester (EEST) to introduce smoke into the EVAP system. Move all EVAP components while observing smoke with the J 41413-SPT High Intensity White Light. Introducing smoke in 15 second intervals will allow less pressure into the EVAP system. When the system is less pressurized, the smoke will sometimes escape in a more condensed manner.
• To improve the visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with the J 41413-SPT .
• Observe the Freeze Frame/Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition occurs that caused the DTC to set. This may assist in diagnosing the condition.

the valve is here "P"
#10 if it leaks running, stuck open rpm can go wild
or the hose to it is cracked

Trouble Code: P0455

EVAP Large Leak Detected

Possible Causes:


EVAP purge solenoid is damaged or it has failed.Fuel tank cap is damaged, missing or the wrong part number.NVLD switch is damaged or it has failed.OK GINA,YOUR MISSION IS TO FIGURE THIS OUT,MESSAGE WILL DESTRUCT WHEN YOU FIX.

Trouble Code: P0446

EVAP Vent Control Solenoid Circuit Malfunction

Possible Causes:


Vent solenoid circuit open, shorted to ground or to power (B+).Vent control solenoid is damaged or has failed..PCM has failed.TSB 00-060 (7/00) contains information related to this code.Trouble Code: P0455

EVAP System Gross Leak (0.080") Detected

Possible Causes:


.EVAP control system pressure sensor is damaged or has failed.EVAP purge solenoid or canister vacuum line loose or off.EVAP purge solenoid is damaged or has failed.EVAP emission canister is dirty, restricted or full of water.EVAP canister vent control valve is damaged or has failed.Fuel tank cap loose, missing or it is the wrong part number.Fuel tank temperature sensor is damaged or has failed.Fuel tank vacuum relief valve is damaged or has failed.Large leak in the EVAP canister or in the fuel tank area.ORVR system is damaged or has a large leak in a component.Refueling control valve is damaged or has failed.Vacuum hose leaking between intake manifold and Purge valve.Here are the codes,take part back and get refund.

Pls provide more as to what you would like to fix?
All your emissions related stuff is on a diagram under your hood. Follow the diagram to the appropriate item your looking for !

trouble shoot P1443 99 ford explorer 4 liter 6 . failed evap pressure sensor. blocked hose between purge valve &fip sensor. evap purge valve stuck closed. where are these sensors and whats the fix?

You DO NOT necessarily need special testing and tools to fix this. Many auto parts stores have scan tools that they'll hook up for free as a diagnostic aide. Your evap system is solely to keep fuel vapors from escaping into the atmosphere when your car is OFF, but you will fail emissions testing with a leak.

CODE PO2401 EVAP SYSTEM LEAK DETECTION PUMP MOTOR CIRCUIT LOW.POSSIBLE CAUSES.EVAP SYSTEM LEAK DETECTION PUMP MALFUNCTION.POOR CONNECTION OF EVAP SYSTEM OR PCM CONNECTOR.PCM HAS FAILED.

Did they explain the fuel evap test to you and what may have caused you to fail? Most smog tests that I've dealt with only test your gas cap and don't actually test your evap system itself. Gas cap is part of your evap system so when the cap fails, you automatically fail your evap system test even though they don't actually test it.

I recommend replacing your gas cap and giving it another shot as the cap will cost $10 to $20...

Trouble Code: P1456


EVAP System Very Small Leak (0.020") Detected

Possible Causes:


EVAP control system pressure sensor is damaged or has failed

EVAP purge solenoid is damaged or has failed

EVAP canister vent control valve is damaged or has failed

Fuel tank cap not tightened properly or the wrong part number

Fuel tank temperature sensor is damaged or has failed

Fuel tank vacuum relief valve is damaged or has failed

Very small leak in the EVAP canister or in the fuel tank area

ORVR system is damaged or has a small leak in a component

Refueling control valve is damaged or has failed

po442 is evap emission control system leak (small) 1 of the lines for emissions is leaking. po455 is-- emission control system leak (large). turn off light with code scanner after it is fixed.