Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP
If you have a gross evap leak it could be the purge solenoid. If it's stuck open when the car is running it will pull the fuel vapors into the intake manifold at all times and not just when it is suppose to. This will cause the rough running and stalling because the engine is basically flooding out.
These could be separate issues as well. The evap leak may not be related, but since you have all this going on at the same time, it seems likely.
Most of the time the best thing to do is have a smoke test done. This will put smoke into the evap system, then they use a large bright light to find the leak. If the leak isn't the purge solenoid, then it should be repaired and then go after the running condition.
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