Where is the vapor canister vent solenoid on my 1999 Monte Carlo ls?

will not be a vapor lock as such but a vacuum in the system caused by a faulty EVAP system vent solenoid
run the fault codes first to determine if vent valve or solenoid of the purge valve

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

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How To Install Replace Vapor Canister Purge Valve 3.4L ...

? 2:42
https://www.youtube.com/watch?v=IPKnoxJCIWk
Jul 9, 2014 - Uploaded by 1A Auto Parts
http://www.1aauto.com/vapor-canister-purge-solenoid/i/1aemx00137 In ... How To Install Replace PCV Valve3.4L 2000-07 Chevy Monte Carlo ...

HERE'S WHAT IT LOOK'S LIKE.Mounted near evaporative canister. http://www.autozone.com/engine-management/canister-vent-valve-solenoid/dorman-canister-vent-valve-solenoid/kia/sorento-2wd/2004/6-cylinders-3-3-5l-mfi-dohc/970779_548862_0

Hello,The problem is that the EVAP system is not able to achieve or maintain vacuum during the diagnostic testThe control module tests the evaporative emission (EVAP) system for a large leak. The control module monitors the fuel tank pressure (FTP) sensor signal to determine the EVAP system vacuum level. When the conditions for running the test are met, the control module commands the EVAP canister purge solenoid valve OPEN and the EVAP canister vent solenoid 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 solenoid 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 decreases too rapidly, the PCM will set the code you now have.So, you either have a stuck open purge valve, a stuck open vent valve, a false reading fuel tank pressure sensor, or a cracked/broken EVAP line.

Did you check the block box connected to the vent solenoid? There's a hose that comes off it that appears to run nowhere, that's the fresh air vent. If it's blocked it won't allow air into the system which will set the trouble code. If that's clear, the vent solenoid itself is bad and needs to be replaced.

Back by your tank, there is a vapor canister with a vent valve on it. That valve is supposed to let vapor from the tank into the canister. Check to see if the valve is working. You can test it by connecting it directly to the battery with some jumper wires. Once in the canister, the vapors are opened to the engine vacuum for burning by the purge valve once the car is warmed up and on the road. If the vent valve is working, but pressure is still building, the problem can be the purge valve at the engine. You can tell this is the problem if the cannister is full of liquid gas. Normally, and depending on the failure mode, these failures would set the engine light. If the light is on, get a scan to see where the problem is. Please let me know if you have more questions, and thanks for using FixYa.

vent valve/canister:

You either have an obstruction in the filler tube or the vent tube on the filler is clogged so it is not allowing air to escape as the gas is going in.

hi there, you see todays cars are so emmision friendly that not even the vapors from your tank can be released into the atmosphere so what they have done is all your vapors are put into a charcoal canister to absorb the vapors and the next time you start the car it has a purge solenoid open and burn the vapors off. if you look around the intake youll see a hose with a green cap follow it back to the charcoal canister and while your doing that just check the hoses and the hoses around the canister to make sure there is no holes or cracks in them and then follow the hose from the canister to the gas tank. if every thing looks good then i would replace the purge solenoid.

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).