Hello everyone. I need your help.
My car is a 2011 Corvette (Base), 6L80, almost 80k miles. Recently, the error P0442 (EVAP small leak) started popping up, I reset it, but after a couple of trips it came back. I reset it again and it hasn't appeared yet, but after some time, a gasoline smell appeared and the message "check gas cap" periodically appeared on the panel - I tightened it a couple of times and the message on the panel disappeared, but the smell remained. I decided to go to the workshop to read the error codes that I have.
I received the following codes, which you can see in the screenshots. As you can see, I already have the error P0455 (EVAP LARGE leak) on the engine - I think I need to make a smoke generator test, but maybe someone has been in a similar situation and knows how to diagnose the problem in other ways?
I also want to say that there are no misfires in ANY cylinder, but the car shakes a little at idle. Also, when I slowly crawl in traffic and release the gas pedal, the car jerks, as if someone is pressing the brake, but It drives normally overall, (I have nothing to compare it to). LONGFT1 and LONGFT2 at idle (I checked only at idle, it is dangerous to do this alone while driving) reaches approximately 11-13%, but it seems that if you raise the RPMs a little, it drops to 5-7%.Nothing lights up on the panel except the tire pressure sensor (By the way, the check engine light is also not on, although there is an error P0455). Everything basically works, but I am confused by all these errors that I see. Does anyone know where to start checking for other errors?
P.s. The air conditioning system was not filled again after the engine repair and I don’t know if it works at all, I haven’t had time for it yet.

 

You will need a factory level or equivalent aftermarket scan tool to diagnose this and you should have one if using a smoke machine as the EVAP vent valve will need to be closed…if fuel trims decrease as RPM’s are raised you most likely have a vacuum leak…if you don’t understand how the EVAP system works you will have trouble diagnosing this.

 

https://www.youtube.com/live/bBdK7GE...JAoIH38WegR6GT

 

You did not say if your longft's are minus or plus. You also have to monitor them while you are driving to know exactly what is happening. If they are minus over 10% it is runing too rich and ECM trying to lean it. That means either one of your EVAP solenoids bad, or your canisters sucking fuel or fumes in to your intake. If they are positive over 10 %, than you have a vacuum leak, like C5 diag mentioned. Good places to check are all EVAP lines coming to your intake. They are plastic Ang get brittle and crack if they are moved around or man handled.

 

Thank you a lot. The reading is negative, I understand that the possible reason is either EVAP solenoids are bad, or canisters are sucking fuel or fumes in to intake? How can I check what exactly is wrong?

 

Unfortunately it sounds like you do not have the equipment to properly diagnose the EVAP system. First you have to monitor the long term ft's while driving, if they are all under 10%, it could be as simple as a bad gas cap. If they are more than the 10%, you need a sophisticated scanner that can do EVAP system test. Unless you are willing to invest up to 1K in scanners your best bet is to find a good vette shop or another shop with proper equipment to do the diagnostics.

 

And the EVAP issue, could also be the valve in the evap canister is stuck open... and would need to replace the EVAP canister... Happened with a couple of my previous GM vehicles..

But the EVAP code would NOT cause all of those other codes man... You have all kinds of issues going on there... you need to take it to a dealer/shop and have things scanned with a GM dealer-level scan tool to figure out all of those issues.

 

Thank you, I will try to order EVAP canister and replace it. Could it also be the EVAP solenoid? Unfortunately, there is no GM dealer in my area, so I will have to just look for a good diagnostician who understands GM.

 

Which valve “INSIDE” the canister is stuck open ??

 

WHY are you ordering a canister if you don't know what the problem is ????...the GM EVAP system is the simplest of all domestic or foreign systems...did you watch the video ??...I would understand how the system works before firing the parts cannon !!....any competent shop should be able to diagnose this...if not they are in the wrong business...BTW, the right fuel tank has to be removed to change the cannister...can you do that ??....you live in Kazakhstan ???....as far as having your car repaired in your country you should be driving a Chevy Cobalt instead..just saying !!…since the Cobalt is a GM product any decent shop should know the EVAP system…what does your fuel tank pressure sensor read with the car off ??...you should have a data PID possibly for this even with a cheap code reader.

 

Dealer will want 5 k for replacing the canister since right tank has to be dropped like C5 diag said. Then they will break the crossover tabs while dropping the tank( they get brittle) even maybe internal lines, and GM does not make replacements anymore. Therefore your car will sit at the dealer for months even maybe more. Get it properly diagnosed then comeback here it could be as simple as one of the 2 solenoids, plugged line, as there are walk arounds depending on the problem.