Pontiac Repair: 03 buick po442, high intensity lamp, vent valve

Question
QUESTION: 2003 buick century 50k 3.1 engine po442 changed gas cap and it came back on

ANSWER: Hi There:

well it can be a lot of things a P0442 is a small evap leak and those ARE HARD TO FIND! If you live in the rust belt like I do I would pay perticular attention to fule filler pile where the cap seat on the pipe. there is a plastic ecge that the cap seals agains that could be damaged or just below that the pipe's rot out and cause a leak. Another possability would be a vent valve for the evap canister those have a tendency to stick and not seal fully and cause leaks. those are the 2 most likely cuase other then the gas cap which you changed And I hope you didn't get an after market one. Any kind of emission part I would tend to stray away from after market parts. Good luck :)


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QUESTION: If I Went To The Shop Would They Be Able To Narrow It Down With Their Computer Where The Problem Is Thanks

Answer
It depends on how good they are. in order to find a small leak issue the shop needs what's called a "smoke machine" it induces a small amount of smoke into the evap system under pressure and then with the use oof a high intensity lamp they can see where the smoke is leaking out of the system causing the code to set. My bet it it's one of the 2 things I mentioned previouly. Not much else goes bad with these.