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Discussion Starter · #1 ·
Hi,

I have a 2012 Hyundai Accent 75,000 miles. Noticed what seemed like reduced engine performance lately (slower acceleration, weird shifting and mpg) and check engine light came on. Scanned the code as P0456 very small evaporator emissions leak.

I checked for any obvious cracking in any hoses, and took out the purge valve to check it (it seemed perfectly fine).

I screwed on the gas cap as tight as it could possibly go also.

Can a very small evap leak even cause engine problems like this? I know larger ones would maybe throw off the fuel air mixture making it run lean and rough etc but seems like a dramatic change for a very small leak.

Does anyone have any recommendations for anything else I can check myself? Or am I stuck taking it to mechanic with a smoke tester?

Also, not sure if this makes a difference but I did hit a pretty huge pothole 2 days before the light came on, figured it might have knocked something loose but can't find anything.

Thanks in advance!!
 

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I screwed on the gas cap as tight as it could possibly go also.
Check the o-ring on your gas cap for cracks. I had a Suzuki that was throwing a similar code. Replacing the cracked o-ring solved that problem.

Can a very small evap leak even cause engine problems like this?
Just a guess, but I think probably not. Anything loading the engine (ie. dragging brakes too much, etc.)?
 

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the evap purge valve/sensor in my 2013 RB it is near here, to test it disconnect the plug, use some cables to bridge the negative to the battery and then put your ear close to the valve while making "taps" with the other cable on the positive (or use a 9v battery), it should sound a "tick" every tap (open/close) try to clean it with some map sensor cleaner
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Discussion Starter · #4 ·
I have tested both those things (gas cap and purge valve), thanks for the recommendations guys. I didn't get far in figuring anything else out yet... is there any way to test for a leak in evap system without a smoke machine? I've read that some people will put 1 or 2 psi pressure on the system and then do soapy water test like you do for a tire. Has anyone tried that before?

Also, I can't see any other reason for the engine sounding so rough/being so weird and no other codes were thrown but I suppose I should check some more basic things. I was wondering if transmission fluid was low or something but apparently it's really tough to get to in a Hyundai Accent because it was meant to last forever or something.

If anyone has any info on DIY smoke tests for this car or something similar to help me find the leak that would be super helpful. Otherwise I'll get it taken in but thanks!
 

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Unless the purge valve were stuck open I don't see how an EVAP problem would affect driveability.
There's something else going on. Electrical I suspect. Also, check fuel trim data.
Monitor battery voltage while driving.
 
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