# Evap Leak on diagnostics **URL:** \ **Category:** NYSpeed Automotive\ **Created:** [August 28, 2008, 11:20am UTC](https://forums.speedlife.net/t/evap-leak-on-diagnostics/54013 "2008-08-28T11:20:16Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![dlatone](https://avatars.discourse-cdn.com/v4/letter/d/b19c9b/32.png) [@dlatone](https://forums.speedlife.net/u/dlatone)\ **Post date:** [August 28, 2008, 11:20am UTC](https://forums.speedlife.net/t/evap-leak-on-diagnostics/54013/1 "2008-08-28T11:20:16Z")
went to auto zone the other day to check my engine light. it came up as an evaporative emission leak. possible causes: defective or loose fuel cap EVAP canister or hose cracked/not connected purge or vent solenoid defective vacuum leak at engine any suggestions on where to go yo get it checked out? id do it myself, but i dont really know what im looking for. and i dont want to get ripped off and be duped into buying 3 sensors and all kinds of crap i dont need. somewhere near cheektowaga or tonawanda would be good. thanks ---
**Author:** ![Dr.Stevil](https://avatars.discourse-cdn.com/v4/letter/d/da6949/32.png) [@Dr.Stevil](https://forums.speedlife.net/u/Dr.Stevil)\ **Post date:** [August 28, 2008, 11:24am UTC](https://forums.speedlife.net/t/evap-leak-on-diagnostics/54013/2 "2008-08-28T11:24:20Z")
to check for a vacuum leak, with the car running, spray carb cleaner/ether over the top of the engine. If the engine revs, you found a vac. leak fuel cap is easy to check… try another one from a friends car to see if it takes care of it. ---
**Author:** ![AKA-FERRARI](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/aka-ferrari/32/7260_2.png) [@AKA-FERRARI](https://forums.speedlife.net/u/AKA-FERRARI)\ **Post date:** [August 28, 2008, 11:25am UTC](https://forums.speedlife.net/t/evap-leak-on-diagnostics/54013/3 "2008-08-28T11:25:03Z")
you need to have a nitrogen vapor test done, is will tell where the evap leak is. most of the time the leak is too small to see with the naked eye. any equipped dealer should have this machine. keep in mind if you go to an independent repair shop…most dont have this tester and send their cars to dealers for this kind of repair. btw, what kind of car? ---
**Author:** ![dlatone](https://avatars.discourse-cdn.com/v4/letter/d/b19c9b/32.png) [@dlatone](https://forums.speedlife.net/u/dlatone)\ **Post date:** [August 28, 2008, 11:35am UTC](https://forums.speedlife.net/t/evap-leak-on-diagnostics/54013/4 "2008-08-28T11:35:30Z")
03 monte carlo ---
**Author:** ![garbs](https://avatars.discourse-cdn.com/v4/letter/g/3d9bf3/32.png) [@garbs](https://forums.speedlife.net/u/garbs)\ **Post date:** [August 28, 2008, 12:04pm UTC](https://forums.speedlife.net/t/evap-leak-on-diagnostics/54013/5 "2008-08-28T12:04:47Z")
I know someone that had this happen when they cross-threaded their fuel cap. Make sure your fuel cap is on right, clear the code, and see if the check engine light comes on again. ---
**Author:** ![dlatone](https://avatars.discourse-cdn.com/v4/letter/d/b19c9b/32.png) [@dlatone](https://forums.speedlife.net/u/dlatone)\ **Post date:** [August 28, 2008, 12:17pm UTC](https://forums.speedlife.net/t/evap-leak-on-diagnostics/54013/6 "2008-08-28T12:17:23Z")
is there any way to clear it without actually clearing it from the checker? i cant disconnect the battery because i will lose my head unit. will this affect my gas milage? i have been noticing a decent drop off (like 4 mpg or so). i would assume that anything with the injection system could hurt it. ---
**Author:** ![Spam16v](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/spam16v/32/5287_2.png) [@Spam16v](https://forums.speedlife.net/u/Spam16v)\ **Post date:** [August 28, 2008, 12:18pm UTC](https://forums.speedlife.net/t/evap-leak-on-diagnostics/54013/7 "2008-08-28T12:18:15Z")
go buy a vent valve, it’s behind your drivers rear tire way up in there… $25-36 retail. you can bench test it if you’d like, two wires and a battery and try to blow through it, when energized if you can blow through it, it’s junk. i’ll put five bucks on it 😉 ---
**Author:** ![Griff](https://avatars.discourse-cdn.com/v4/letter/g/f19dbf/32.png) [@Griff](https://forums.speedlife.net/u/Griff)\ **Post date:** [August 28, 2008, 12:28pm UTC](https://forums.speedlife.net/t/evap-leak-on-diagnostics/54013/8 "2008-08-28T12:28:42Z")
this just happened on my s10 2 weeks ago. unhook the batter for 10 minutes and then hook it back up. should clear the code. if it pops back up its something, if not you’re good ---
**Author:** ![JayS](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/jays/32/15375_2.png) [@JayS](https://forums.speedlife.net/u/JayS)\ **Post date:** [August 28, 2008, 1:58pm UTC](https://forums.speedlife.net/t/evap-leak-on-diagnostics/54013/9 "2008-08-28T13:58:32Z")
On the evap leak codes I always pop the gas cap off and put it back on, making sure it’s good and tight. Clear the code and see if it comes back. Make sure you don’t get gas with the car running because that can trip the evap code as well. As for clearing it, your options are using a scanner or remove the battery for long enough to clear the code. Since you said you don’t want to lose your radio that leaves you just with option 1. There aren’t any pin shorting tricks like in the old OBDI days that I know of for OBDII. I’m sure autozone can clear it since any scanner capable of reading the code is capable of clearing it. Just a warning though, if you’re doing this because your inspection is due… If you clear the code and head immediately to the inspection you fail. Clearing it resets all the readiness monitors and if you only take short trips it can take a while for them all to complete their tests. ---
**Author:** ![dlatone](https://avatars.discourse-cdn.com/v4/letter/d/b19c9b/32.png) [@dlatone](https://forums.speedlife.net/u/dlatone)\ **Post date:** [August 28, 2008, 2:51pm UTC](https://forums.speedlife.net/t/evap-leak-on-diagnostics/54013/10 "2008-08-28T14:51:52Z")
i did the gas cap thing before and it didnt clear. but now it looks like it went away. hopefully it doesnt come back ---
**Author:** ![AKA-FERRARI](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/aka-ferrari/32/7260_2.png) [@AKA-FERRARI](https://forums.speedlife.net/u/AKA-FERRARI)\ **Post date:** [August 28, 2008, 2:55pm UTC](https://forums.speedlife.net/t/evap-leak-on-diagnostics/54013/11 "2008-08-28T14:55:42Z")
Also if you fuel the vehicle with it running, it will sense a leak and turn the light on. ---
**Author:** ![Pauly](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/pauly/32/7493_2.png) [@Pauly](https://forums.speedlife.net/u/Pauly)\ **Post date:** [August 28, 2008, 3:33pm UTC](https://forums.speedlife.net/t/evap-leak-on-diagnostics/54013/12 "2008-08-28T15:33:42Z")
> [@JayS](#): > > Just a warning though, if you’re doing this because your inspection is due… If you clear the code and head immediately to the inspection you fail. Clearing it resets all the readiness monitors and if you only take short trips it can take a while for them all to complete their tests. Jay has knowledge ---
**Author:** ![AKA-FERRARI](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/aka-ferrari/32/7260_2.png) [@AKA-FERRARI](https://forums.speedlife.net/u/AKA-FERRARI)\ **Post date:** [August 28, 2008, 3:50pm UTC](https://forums.speedlife.net/t/evap-leak-on-diagnostics/54013/13 "2008-08-28T15:50:16Z")
> [@Pauly](#): > > Jay has knowledge true, but there is a certain driving procedure for readiness. Involves a combo of highway/stop and go/city driving. Just drive it normal for a couple of days and it should be ready ---
**Author:** ![psychopjv](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/psychopjv/32/7251_2.png) [@psychopjv](https://forums.speedlife.net/u/psychopjv)\ **Post date:** [August 28, 2008, 10:04pm UTC](https://forums.speedlife.net/t/evap-leak-on-diagnostics/54013/14 "2008-08-28T22:04:28Z")
so basically you have a p0440. did you recently get gas and forget to tighten? a small evap leak is i believe in the .020 area. As stated a nitrogen smoke machine (electric bong) is needed to properly test the system for holes. ---
**Author:** ![nitroinsane](https://avatars.discourse-cdn.com/v4/letter/n/d26b3c/32.png) [@nitroinsane](https://forums.speedlife.net/u/nitroinsane)\ **Post date:** [August 29, 2008, 12:41am UTC](https://forums.speedlife.net/t/evap-leak-on-diagnostics/54013/15 "2008-08-29T00:41:53Z")
> [@AKA-FERRARI](#): > > you need to have a nitrogen vapor test done, is will tell where the evap leak is. most of the time the leak is too small to see with the naked eye. > any equipped dealer should have this machine. keep in mind if you go to an independent repair shop…most dont have this tester and send their cars to dealers for this kind of repair. btw, what kind of car? what he said