EVAP leak

[MarlboroMan]

Several months ago my truck was idling rough, like a sporatic little shimmy. Also, in high gear, at low rpm, when trying to accelerate, it would buck like a misfire. You had to give it significant throttle to get it to down shift and get past the bucking. CEL light came on and it was a 'EVAP small leak'. I did find a small crack in the hose near the canister. Replaced it and as I suspected it didn't fix anything cause I wasn't confident EVAP leaks could cause problems like this. I deleted the code about a month ago and now the same EVAP code came back. It sounds more like an ignition issue and the EVAP is just a coincidence, but I'm wondering why my CEL is not picking up misfires or anything. I just replaced wires/cap/rotor/plugs about a year ago. Doesn't mean that something isn't faulty, but I inspected them and changed plugs and everything seems fine. Has anybody ever had EVAP issues and can the problems be this noticeable? I wouldn't think an EVAP leak would cause bucking or rough idle like that.

 

[oldmodman]

Most well equipped dealerships use a smoke generating machine to pressurize the evap system. Then they just follow the smoke leaking from whatever has failed.

 

[greenstang1313]

i worked at autozone a while back and EVAP codes are almost always just a bad fuel cap. changing your fuel cap wont fix your engine problem but at least your code will shut off.

 

[MarlboroMan]

Most well equipped dealerships use a smoke generating machine to pressurize the evap system. Then they just follow the smoke leaking from whatever has failed.

I know how they do it. I'm asking if EVAP leaks are usually relatively unnoticeable or not so I don't have to spend a bunch of money to find crack in a hose that I can find myself. I've never experienced an EVAP leak so I don't know if even the worse EVAP problems can cause rough idle or jerky acceleration like that.

i worked at autozone a while back and EVAP codes are almost always just a bad fuel cap. changing your fuel cap wont fix your engine problem but at least your code will shut off.

Yeah, it's not the cap. And I've already deleted the code once and it came back two months later then went off after about a week. I'd like to pinpoint the source of my rough idle so I can determine if the EVAP occurring around the same time is just a coincidence.