evap vent solenoid

quick question. Can a EVAP vent solenoid mess with your fuel trim if its not working correctly. So I believe the vent is naturally open. Mine is reading closed all the time. I can command it with my lab top to open. I am chasing a vacuum leak and ive narrowed it down to the EVAP system. I just replace fuel cap and well it mad a hell of a difference. go figure after replacing every line in the dam car almost. But my ltft seem to be still a little high and it creeps up. At temp its around 9.7. I did notice that my vent never opens. Like I said I can command it to open, watch it build vacuum, sensors seem to move with vacuum increase.

Im currently in the middle of tuning the car but dont want to go any farther until I get this leak under control. Anyone with any tips that would be greatly appreciated. Thanks in advance.

2013 Ats 2.0t. E85 downpipe, exhaust, cold air, larger fuel pump lobe, catch can

How have you determined you have a vacuum leak, and more specifically that it's related to the EVAP system?

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Originally Posted by tunerpro

How have you determined you have a vacuum leak, and more specifically that it's related to the EVAP system?

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My Ltft are or were extremely high. Maf was reading around 1300 htz. I just started isolating parts of the vacuum system. When I blocked off the EVAP system I was able to get my numbers somewhat back to normal.

It started with what felt like turbo surge at WOT. Wound up finding fuel in my crank case. Replaced HPFP and sensor. Fixed the fuel issue but it was still pulling air in. I smoked it. tried propane and I couldn't find anything. Isolated the motor mounts and still no change. Only when I isolated the EVAP system is when I noticed a change in my fuel trims and MAF readings

Thanks for clarifying.

Yes, an EVAP system leak could / would certainly skew your trims since it represents unmetered air / vapor getting into your engine. It is important to keep in mind both that the ECM occasionally tests the EVAP system by commanding the valve open and measuring the change in the trims / O2 sensor signal, and also performs vapor purge events which can skew the trims as well. Generally speaking, the fuel trim code diagnostics are suspended while either a self-test or a purge event is occurring, so you may see highly skewed trims with an absence of a P0171/P0172 DTC, and that may be normal.

Having said that, if you're certain your EVAP system should NOT have been flowing when you isolated it, then, yes, it sounds like you've found an issue. I would have expected the ECM to set P045x DTCs for this, however.

so is the system normally closed or open? I did get a leak code prior to the gas cap but havent got one since. I believe the car is bi polar. took two logs today and during the day she just dont seem happy. Now at night time its a totally different story.... Runs great and numbers look good. Im ordering intercooler this week to help with IAT. Crazy that dam vacuum leak drove me to drink. Here it was the gas cap. I still think there is an issue with EVAP vent. @tunerpro I appreciate the feed back man.

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Originally Posted by Djc79

so is the system normally closed or open? I did get a leak code prior to the gas cap but havent got one since. I believe the car is bi polar. took two logs today and during the day she just dont seem happy. Now at night time its a totally different story.... Runs great and numbers look good. Im ordering intercooler this week to help with IAT. Crazy that dam vacuum leak drove me to drink. Here it was the gas cap. I still think there is an issue with EVAP vent. @tunerpro I appreciate the feed back man.

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Are you asking about the Purge Solenoid or the Canister Vent Solenoid? I just read through the EVAP system info for a 2010 Camaro yesterday and the Canister Vent is normally open.

Canister vent is closed when the key is on, open when the key is off. The ecm monitors the fuel tank pressure sensor, and vents excess tank vapors through the engine to be combusted, using the purge solenoid on the engine. That's how the system works. If your purge solenoid is stuck open, the one on the engine, it will pull fuel through the evap lines by engine vacuum. The vent valve on the canister shouldn't really cause any fueling issues because it vents tank pressure through the charcoal canister, to the atmosphere. Unless of course, it's stuck open.

The cansiter vent is meant to be open when the car is off, so you can fuel the car, and to prevent the fuel tank from rupturing when sitting.If it's closed, or stuck closed, the fuel filler at the gas station will click on and off repeatedly when you're trying to fill it. Also, over filling your gas tank, by not stopping when the pump clicks off, is generally how people destroy their evap systems and not realize it.