Bad idle need help
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2nd Gear
Joined: Mar 2024
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Bad idle need help
Hi I have a 2005 f150 4.6l I keep getting p0446 code evaporative emission control system (EVAP) vent control circuit malfunction (keeps saying vent stuck open) so I went and bought the evap unit and replaced it but still has the same code and horrible idle. I can only move the truck for a very little amount of time and when I pull forward it will run ok till I try to go up a hill it will stall out. So far I changed the evap cannister the fuel injectors the coil packs and the spark plugs. I think it's an air leak somewhere but I have no idea any help will be great thanks in advance
Last edited by Rickyrick7; Mar 20, 2024 at 01:05 AM.
Fleet Mechanic
Joined: Apr 2016
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This circuit is best tested with a bidirectional scanner . You can send a command for the pcm to close vent solenoid which then you can also use a test light on wiring . Otherwise you are stuck with the whim of the pcm deciding to pull a test on the system with vacuum going down the road . Bidirectional scanners are not cheap but once you are up in there you want to make sure it can function all the way to the pcm , new vent solenoids can be bad right out of the box . New does not mean good .
If you do replace it you want to also make sure it doesn't leak thru by using air or blowing thru it when energized . It only closes when energized. so make sure it will pass air when deenergized . It must be open when filling tank , gas goes in air must go out vent solenoid the carbon cannister cleans the air as it goes out .
If you do replace it you want to also make sure it doesn't leak thru by using air or blowing thru it when energized . It only closes when energized. so make sure it will pass air when deenergized . It must be open when filling tank , gas goes in air must go out vent solenoid the carbon cannister cleans the air as it goes out .
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