2008 Mazda 3- check engine light came on 2 codes

[travisfraughton]

New to the forum
ok, so my wife's new 2008 mazda 3 just had the engine light come on, i sent her to autozone while I'm at work today to get the codes pulled. She called me with 2 codes

P0455- (possible fuel leak) - i understand that if the gas cap isn't tight this can cause the light to come on fairly easily in these cars, so i am not super worried about it except the fact that it pulled another code

P0171- (Air fuel ration problem) - seeing as how it is also consistent with the gas cap issue, i hope it's not a purge valve, canister or anything else, I am hoping it's just the stupid gas cap thing. I'm going to reset it tonight when i get home (standard disconnect the negative post on the battery right?) and see if the light comes back. I guess she said she didn't think she had tightened the cap until it clicked the last time she got gas, so I really think that's what it is, but ...

I'd really like to know if anyone else has had these 2 codes pulled simultaneously and what the issue was for you.
I appreciate your feedback

[cali_axela]

Yep, probably just the gas cap. Ensure it's fully engaged, reset ECU in the method you expected which is correct, and see if it comes back or not; probably won't

[travisfraughton]

ok, so yesterday night I was driving home in the wife's car, and the check engine light came on again.
I ran the codes this morning and only got 1 code back. the same P0171, that it was running lean, bank 1 .
Same code as the last time.
So immediately I figured it's the same thing, just loose gas cap.
But this morning after I took it to autozone, I stopped to fill up the gas. After I filled up, (I put in 87 octane instead of 85 which is what my wife usually puts in it.) it wouldn't start. It would just crank. Tried several times and after several tries it fired and ran fine.
So I'm wondering,
A: why would it wait until my wife had run through almost an entire tank of gas to pop the code if it was a loose gas cap.
and
B: why did it all of a sudden have a hard time starting?

The possible problems the code refers to are
1-low fuel pressure
2-large vacuum leak
3-dirty/defective MAF sensor
4-engine mechanical condition

Anyone had the same or similar?
I cleared the code and will wait to see if the code comes up again.
Thanks.

[ekanddsm]

you have a classic case of a stuck open purge solenoid.

That causes a evap leak when the car is turned off.

if it is stuck when you refuel, it puts alot of fuel vapors inside the intake manifold, causing a rich mixture upon startup.

hence why it took so long to refuel.

[travisfraughton]

did you mean why it took so long to restart? it didn't take any longer than usual to refuel.

Any ideas for the solution on that?

[07mazzy3]

yea when they first act up, they take forever to start! and another word of advice! dont use 85 octane! use 87 @shell or exxon! i have63k miles on my car and run the crap out of it and didnt need a purge valve till 62kmiles!

[john_in_the_lbc]

personally, i can think of no reason to use higher octane than the car is designed for.%