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Bill, Chevy Technician
Category: Chevy
Satisfied Customers: 1776
Experience:  GM Certified Master Technician
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Ron, I have a 2008 Malibu CLASSIC with a P0455 evap code. I

Customer Question

I have a 2008 Malibu CLASSIC with a P0455 evap code. I have read thru your earlier thread for this car/code but still have a couple questions.
Backround: I have an aftermarket fuel cap, but it has worked ok for the last couple years.
I recently replaced the Fuel Level Sensor, so this may be a self inflicted problem.
I am not the general driver if this car, but I am told that for a day or two after a fill up there is episodes of rough idle and stalls at the stop light. After a couple days of driving (60-100 miles) the problem seems to go away.
I do not think the problem occured before I was in to replace the level sensor but cannot be sure of that.
Seems like I am flooding the evap can at fill up, but that is just a guess on my part. Why else would the problem go away?
Also, there is a vent hose that goes to the top of the fill tube - just below the cap. Does that go to the evap can and it the only hose that feeds the evap can?
Thanks for the help.
Submitted: 1 year ago.
Category: Chevy
Expert:  Bill replied 1 year ago.

Did you still need help with this concern? I can send a vacuum diagram if you wish that shows the fuel tank system layout. It is not possible to find the leak without special test equipment however that being said the likely fault is the evap purge valve being stuck open. If there were a leak in the system in another location, it should not affect vehicle drivability. The fact that you are having starting issues after refueling points towards the cannister being purged of fuel vapor when it is not commanded to purge. The evap purge valve is likely stuck open which would cause both a starting issue after fueling and an evap leak resulting in the p0455


Expert:  Bill replied 1 year ago.

Fuel tank diagram