Been chasing my tail here on an evap code P1430. No CEL
I have replaced the solenoid valve on the top as well as the solenoid on the canister. Still no luck.
Now the solenoid valve on the top is fluttering (open and closing quickly).

When I remove the top valve and hook it up to a battery it opens and closes without any problems, I put it back and start the car it starts to flutter after a minute or so. It's as though the PCM is sending a pulsing signal. Is there possibly a sensor that is gunked up and not seeing vacuum?

I'm pulling my hair!!!!

2016 F150 XLT Sport 5.0

 

Fluttering is normal for the canister purge valve. The pcm commands a percent open, and accomplishes it by rapidly varying the amount of time it is open.

 

Thank you so much for the reply!!
I guess I need to wait it out to see if it clears.

Where does the PCM detect whether there is vacuum? I'm thinking the sensor is gunked up???

 

PCM detects EVAP issues using the FTP sensor, near the fuel tank.

Double check your code, the one you listed is not an evap issue. What you you mean there isn't a CEL light? EVAP issues almost always trigger it. Is the code maturing, but never gets to the point where it is confirmed? Intermittent issues can be a challenge to diagnose. Confirm code and we can give you a list of things to check.

This is a good video that explains the operation of the evap system.

 

I apologize the code is not P1430.... it is P1450 - Unable to Bleed up Fuel Tank Vacuum

I have no CEL, the code P1450 is in Permanent Trouble Codes according to my reader.

I am starting to think there's a small leak somewhere.....

 

This is what my service manual for my 2015 shows:
P1450 - Unable To Bleed Up Fuel Tank Vacuum
Description: This DTC sets when the evaporative emission (EVAP) running loss monitor detects excessive fuel tank vacuum
with the engine running, but not at idle.
Possible Causes: • EVAP purge valve stuck open
• Blockages or kinks in the EVAP canister tube or EVAP canister purge outlet tube between the fuel tank,
the EVAP purge valve and the EVAP canister
• Fuel filler cap stuck closed, preventing vacuum relief (if equipped)
• Capless fuel tank filler pipe damaged, preventing vacuum relief (if equipped)
• Contaminated fuel vapor elbow on the EVAP canister
• Restricted EVAP canister
• EVAP canister vent valve stuck partially or fully closed
• Plugged EVAP canister vent valve filter
• VREF circuit open
• Damaged FTP sensor
Diagnostic Aids: Visually inspect the EVAP canister inlet port, EVAP canister vent valve filter, and EVAP canister vent hose
assembly for contamination or debris.
Check EVAP purge valve for vacuum leak.

 

First, I want to thank you for the check list on helping me fix this problem!!! I appreciate your time and effort.

I crawled under the truck and was disconnecting the lines from the evap canister to begin checking for leaks and cracks. I opened the fuel door and took a good look at the Easy Fill cap and low and behold I noticed a small piece missing from the inside of the cap where it seals with the flap.

I grabbed a thin latex glove and wadded it up to seal the opening as best I could. After starting the vehicle I noticed the purge valve stopped flapping and the car didn't stumble when coming to a stop during a short 10 mile drive.

See pic below....Now I have to figure out how to replace it.

 

Still getting code...will check lines then FTP sensor

 

I have been troubled with this code P1450(unable to bleed fuel tank vaccum) and still have not found a solution. I have changed the purge flow solenoid as well as the vent solenoid attached to the charcoal canister box. Forsccan data shows 3D 81(blocked evap system line-fault confirmation test) not ready, and 3D 82(vapor blocking valve perfromance) not ready. For some reason it is never able to test. Any idea of what you think can be causing this?