Code reads p0497

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

purge Valve replacement........

https://www.youtube.com/watch?v=1TR9BoHhrJU

DTC P0497: Evaporative Emission (EVAP) System No Flow During Purge
Circuit/System Description
The control module tests the evaporative emission (EVAP) system for a large leak, or a stuck closed EVAP canister purge valve. The control module monitors the fuel tank pressure (FTP) sensor signal to determine the EVAP system vacuum level. When the conditions for running are met, the control module commands the EVAP canister purge valve OPEN and the EVAP vent valve CLOSED. This allows engine vacuum to enter the EVAP system. At a calibrated time, or vacuum level, the control module commands the EVAP canister purge valve closed, sealing the system, and monitors the FTP sensor input in order to determine the EVAP system vacuum level. If the system is unable to achieve the calibrated vacuum level, or the vacuum level increases too slowly, a DTC sets.

Diagnostic Aids
• 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.

Under car,usually mounted near or in front of gas tank

https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&cad=rja&uact=8&ved=0ahUKEwiWp7rZtOfKAhVBlh4KHY1RAwYQtwIINTAG&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DQIlti3aZ22M&usg=AFQjCNEz4TLhC8cVKeIar-IctwksFPqv_g Repair Guides Components Systems Evaporative Emission Control System... https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=11&cad=rja&uact=8&ved=0ahUKEwjQ4dL_tOfKAhVCGx4KHaITC3w4ChAWCBowAA&url=http%3A%2F%2Fcommunity.cartalk.com%2Fdiscussion%2F2290225%2F01-olds-alero-evap-problem-getting-choked-out-by-gas-fumes&usg=AFQjCNEyLR6NegYlup_S2N6z_mGccu_DFA&bvm=bv.113370389,d.dmo

code p 0497 refers to evaporative emission system ---low purge flow====causes ---wiring---EVAP valve ---hoses blocked ---mechanical fault

Section 03-13: Evaporative Emissions 1995 Town Car, Crown Victoria, Grand Marquis Workshop Manual DESCRIPTION AND OPERATION Evaporative Emission Canister Fuel vapor emitted through the evaporative emission valve (9B593) is stored in two evaporative emissions canisters (EVAP canister) (9D653) . I think you should have 2 engine vacuum lines, one for each canister.


Evaporative Emission Canister Purge Valve


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Evaporative Emission Tube Shut Off Valve The evaporative emission tube shut off valve (9G332) is located in-line between the evaporative emission valve (9B593) and the evaporative emissions canister (EVAP canister) (9D653) . The evaporative emission tube shut off valve control valve is mounted on the fuel tank (9002) by an integral bracket. The evaporative emission tube shut off valve closes the flow path from the evaporative emission valve to the evaporative emissions canister during refueling to prevent overfilling of the fuel tank .

Evaporative Emission Tube Shut Off Valve

what codes?

The vacuum lines run from the canister to the intake manifold. One is the purge hose to deliver stored fuel vapor to the intake to be burnd when engine is warm and you are crusing at part throttle. The other line is the vacuum line to operate it.

Fuel Vapor Valve, Aerostar (4.0L Engine) The evaporative emission valve (9B593) uses a small orifice, 1.83mm (0.072 inch), that allows vapors to pass into the vapor line running forward to the evaporative emissions canister (EVAP canister) (9D653). This evaporative emission valve mounts directly into the fuel tank (9002) using a fuel vapor separator seal. Fuel vapors trapped in the sealed fuel tank are vented through the orificed evaporative emission valve. The vapors from the fuel tank leave the evaporative emission valve through a single vapor line and continue to the evaporative emissions canister in the engine compartment for storage.
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Fuel Vapor Canister Purge Regulator Valve, Aerostar, Ranger Removal and Installation

1. Disconnect wire harness from evaporative emission canister purge valve (EVAP canister purge valve) (9C915).
   

1. Disconnect wire harness from thermistor.
   

1. Disconnect evaporative emission canister purge valve assembly from fuel vapor canister and throttle body.
   

1. To install, reverse removal procedure.
   

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You likely won't notice any drivability problems. P0442 indicates a fuel vapor leak in the EVAP control system. It means a very small leak has been detected. In fact, the leak can be from a hole as small as 0.04" in diameter. 
The (EVAP) emission control system prevents the escape of fuel vapors from a vehicle's fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage.
Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine.

With a P0442, the most common repair is to Remove and reinstall the gas cap, clear the codes, and drive for a day and see if the codes come back. Otherwise, replace the gas cap, or Inspect the EVAP system for cuts/holes in tubes/hoses.

Good luck and hope this helps

The ORVR (On-Board Refueling Vapor Recovery) system consists of a unique fuel tank, flow management valve, fluid control valve, one-way check valve and vapor canister.

The ORVR (On-Board Refueling Vapor Recovery) system is used to remove excess fuel tank vapors. This is done while the vehicle is being refueled..

Fuel flowing into the fuel filler tube (approx. 1 inches I.D.) creates an aspiration effect drawing air into the fuel fill tube. During refueling, the fuel tank is vented to the EVAP canister to capture escaping vapors. With air flowing into the filler tube, there are no fuel vapors escaping to the atmosphere. Once the refueling vapors are captured by the EVAP canister, the vehicle's computer controlled purge system draws vapor out of the canister for the engine to burn. The vapor flow is metered by the purge solenoid so that there is no, or minimal impact on driveability or tailpipe emissions.

As fuel starts to flow through the fuel fill tube, it opens the normally closed check valve and enters the fuel tank. Vapor or air is expelled from the tank through the control valve and on to the vapor canister. Vapor is absorbed in the EVAP canister until vapor flow in the lines stops. This stoppage occurs following fuel shut-off, or by having the fuel level in the tank rise high enough to close the control valve. This control valve contains a float that rises to seal the large diameter vent path to the EVAP canister. At this point in the refueling process, fuel tank pressure increases, the check valve closes (preventing liquid fuel from spiting back at the operator), and fuel then rises up the fuel filler tube to shut off the dispensing nozzle.

Continuous Memory Diagnostic Trouble Code (DTC) P0442 indicates that a fuel vapor leak has been detected [as small as 0.10 cm (0.04 inch)] in the Evaporative Emission (EVAP) system.
Note: Prior to performing the following diagnosis inspect the Canister Vent Solenoid (CV) for contamination. A situation may exist where contamination holds open the Canister Vent (CV) solenoid enough to set DTC P0442 and also plugs the port to atmosphere enough to keep system from being vented quickly.

• After market parts and accessories nonconforming to the EVAP system specifications.
• Damaged, cross threaded or loosely installed fuel filler cap.
• Small holes or cuts in fuel vapor hoses/tubes (EVAP canister tube, EVAP canister outlet tube or EVAP return tube) in the EVAP system.
• Loose fuel vapor hose/tube connections to EVAP system components.
• EVAP system component [EVAP canister purge valve, fuel tank pressure (FTP) sensor, canister vent (CV) solenoid, fuel vapor control valve tube assembly or fuel vapor vent valve assembly] seals leaking.
• CV solenoid partially open when commanded closed.
• EVAP canister leaking.
• Check for presence of fuel filler cap.
• Verify that the CV solenoid is properly seated on the EVAP canister (if possible).
• Visually inspect for cut or loose connections to fuel vapor hoses/tubes in following locations:
  • EVAP canister to EVAP canister purge valve.
  • EVAP canister to fuel vapor vent valve assembly.
  • fuel vapor control valve tube assembly to fuel tank (if applicable).