P0455 code, NOT gas cap!
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Joined: Aug 2010
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From: Cumming, GA
P0455 code, NOT gas cap!
I've got a 98 Expy 5.4L with 262,000 miles on it. Engine light came on about a week ago giving the P0455 code (EVAP system leak, large) and until yesterday it didn't have any symptoms. Now just OCCASIONALLY, not constantly, it will idle rough and skip/hesitate anywhere below about 1,500 rpm, and the exhaust smells odd. Any common problem this might be? I say it's not the gas cap cause I saw a thread elsewhere about this same code and people suggested that's what it was. I sincerely doubt a leaky gas cap would cause it to run rough...
Logistics Pro
Joined: Jan 2005
Posts: 3,534
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From: penn twp.
can you describe the smell other than odd. i.e.( sweet, rotten egg like, raw sewage like.) anything like that would help. other than that i'd say to start checking all your vaccum linesand hoses for small holes or kinks. take a good look at the evap. canister, fuel filler neck,and yes the fuel cap for signs of corrosion, cracks clogs or holes. other than that i'd say you'd probally have to take it to a good shop or dealer to have it checked out using a nitrogen smoke machine. since even though the code says it's a large leak it still maybe so small you won't see anything wrong just by looking for it.hope this helps. something else you might want to take agood look at is your egr tube, they often times rust through and give you a bunch of pin holes and may cause your problem.
Hotshot
Joined: Jan 2004
Posts: 19,760
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From: St Louis
A P0455 code means that the PCM ordered the canister vent (CANV) valve to close, then opened the canister purge (CANP) valve to apply manifold vacuum to the top of the fuel tank. It then monitors the fuel tank pressure sensor, mounted on the top of the tank, to see if the airspace goes into vacuum within the prescribed period of time.
A failure of this test is usually due to something causing a faulty seal with a loose or damaged gas cap being the most common reason. The post above gives some good tips on what to check as a visual exam. One thing to add to the list is to check the hose and tube for the CANV valve and the CANV valve itself. Mud from off-roading or from nests made by certain insects, wasps especially, can jam the CANV valve and keep it from closing.
If a visual exam and basic troubleshooting doesn't pan out, you will need to seek the services of a shop with a smoke machine. Injecting very low pressure smoke (harmless and safe) will allow the technician to quickly locate the source of any leak in the evaporative emissions system.
A failure of this test is usually due to something causing a faulty seal with a loose or damaged gas cap being the most common reason. The post above gives some good tips on what to check as a visual exam. One thing to add to the list is to check the hose and tube for the CANV valve and the CANV valve itself. Mud from off-roading or from nests made by certain insects, wasps especially, can jam the CANV valve and keep it from closing.
If a visual exam and basic troubleshooting doesn't pan out, you will need to seek the services of a shop with a smoke machine. Injecting very low pressure smoke (harmless and safe) will allow the technician to quickly locate the source of any leak in the evaporative emissions system.
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Charger73400
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Jan 23, 2006 08:24 PM
