Expedition & Navigator1997 - 2002 and 2003 - 2006 Ford Expedition and Lincoln Navigator
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HX18 DTC P0446 OR P1450: CHECK FOR VISUAL CAUSES OF EXCESSIVE FUEL TANK VACUUM
Continuous Memory Diagnostic Trouble Code (DTC) P0446 or P1450 indicates that Self-Test has detected the Evaporative Emission Control System has excessive fuel tank vacuum. Also, a DTC P0446 indicates a vent control malfunction.
-- EVAP canister purge outlet tube (EVAP canister purge valve to EVAP canister) blockages or kinks.
-- EVAP canister tube (fuel tank to EVAP canister) blockages or kinks.
-- Fuel vapor elbow on EVAP canister contaminated.
-- Restricted EVAP canister.
-- Canister vent (CV) solenoid stuck closed (partially or fully).
-- Plugged or contaminated CV solenoid filter.
-- EVAP canister purge valve stuck open.
-- Fuel filler cap stuck closed (no vacuum relief).
-- VREF circuit open in fuel tank pressure (FTP) sensor.
-- Damaged FTP sensor.
If the EVAP canister-CV solenoid and fuel tank assemblies are not accessible to perform the following step, GO to the Powertrain/Engine Group, Evaporative Emissions Section in the Workshop Manual for removal procedures.
l Check for kinks or bends in the fuel vapor hoses/tubes (EVAP canister purge outlet tube and EVAP canister tube).
l Visually inspect EVAP canister inlet port, CV solenoid filter and canister vent hose assembly for contamination or debris.
l Check CV solenoid filter for blockage or contamination.
l Is a fault indicated?
REMOVE any contamination or debris around fuel vapor hoses/tubes and EVAP canister- CV solenoid assembly. REMOVE kinks or bends in EVAP canister purge outlet tube, EVAP canister tube and canister vent hose assembly. GO to «HX19».
And have you ever followed the procedure (exactly) to its conclusion?
If so, what was called out as the diagnosis?
If not, why not? There's no substitution for actually going through the process to find what works and what doesn't.
Yes I have looked it over and over and over. It just seemed like people copy and paste the procedure thinking it will solve the problem. I don't have a fancy rotunda evap tester doohickey so I couldn't run those tests. I did monitor EVAP PDC and FTP_V and it came out clean (voltage was 2.7V during 0% purge duty cycle). The van is a 2003 with 25k miles, no reason for any valve failures or debris/clogs in a sealed system. I visually examined all the hoses for kinks etc... and found nothing. If the hoses were leaky, I wouldn't hear a fart/burp from the gas cap. I just figured it was a common enough problem that there was a common denominator.
Short of just replacing the purge valve, vent solenoid, and the vapor valve, I'd just be doing exploratory surgery.
My check engine light came on this morning. I checked with Autozone for the code and pulled the P1450. My truck has been feeling as if it is missing, or misfiring over the last couple of months, but there have been no codes until this morning. Will this "Inability of Evaporative Emission Control System to Bleed Fuel Tank" cause any symptoms, or problems? I have a 99 f150 5.4L. Thanks for any info!
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