98 Cavalier stalling/poor idle

I have been having problems with my 98 Cavalier 2.2 liter since I got it three years ago. It seems like every year between February and April I have to deal with stalling and poor idling. It only happens when we have a full tank of gas. The check engine light will turn on and then it will eventually turn off by itself when we drive the car a few times. I have taken it countless times to the garage and they can never find anything wrong with it. We always use dry gas, but that does not seem to help. Once we use about 2 gallons of gas, the car returns to running fine. I took it to autozone and had them run the computer on it a couple weeks ago and it showed a 404 error. But the light turned off afterwards. Now it is acting up again, right after we put in a new tank of gas. It stalls and drives rough when we are under 40mph or stopped at a stoplight or intersection.

I have been having problems with my 98 Cavalier 2.2 liter since I got it three years ago. It seems like every year between February and April I have to deal with stalling and poor idling. It only happens when we have a full tank of gas. The check engine light will turn on and then it will eventually turn off by itself when we drive the car a few times. I have taken it countless times to the garage and they can never find anything wrong with it. We always use dry gas, but that does not seem to help. Once we use about 2 gallons of gas, the car returns to running fine. I took it to autozone and had them run the computer on it a couple weeks ago and it showed a 404 error. But the light turned off afterwards. Now it is acting up again, right after we put in a new tank of gas. It stalls and drives rough when we are under 40mph or stopped at a stoplight or intersection.

Don't recognise the code 404. Wasn't 440 was it? Tha would be the EVAP system. I tcould be as simple as a faulty gas cap. When you fill the tank it may not be able to relieve the vaccuum using the gas causes and therefore creats a fuel starvation problem as the fuel pump is working overtime. When this occurs, try lossening the gas cap and then immediately replace it. If that works then there's your problem. Let me know on the code.

PO404 : Exhaust Gas Recirculation Control Circuit Range/Performance

Would that mean my EGR vavle needs to be replaced? Or could it be something else....

PO404 : Exhaust Gas Recirculation Control Circuit Range/Performance

Would that mean my EGR vavle needs to be replaced? Or could it be something else....

Oh right ok. Yeah it could be that the valve has gone but these aren't cheap! would check all around it first! Last time I know the EGR was about $300CDN! But it could be the problem. It puts exhaust gasses directly into the intake manifold to cool the combustion event and could be poutting too much in!