1995 Cavalier 2.2 rough idle and stalling

y son drove about 500 miles last Friday night. About halfway he got off the highway for a "pit stop" and when he came to a stop at the light at the exit ramp the car stalled. He had to hold his foot down
on the gas to get it to start. For the rest of the trip he had to put the car in neutral and give it a little gas to keep it from stalling at stop lights and stop signs. There was an continues to be no "check engine" light.
I have replaced the fuel filter, replaced the spark plugs (two were burned quite badly), replaced the spark plug wires, cleaned the throttle body including the passage to the IAC, removed the IAC and cleaned it wtih throttle body cleaner (it was quite dirty on and around the plunger that goes through the orifice), and replaced a couple of vacuum lines (I found one off) and one dried and cracked.
Now...it will start cold with now trouble. It will idle pretty well. However, when it sits and idles...or is driven and then stops...it develops rough idle. It it idles under a load (with the a/c on) it idles rough and stalls. Every time it stalls...you have to hold the gas down to get it to start.
I have looked for a way to get the codes out, if there are any, without going to a shop and having it scanned. I found one on line...but..it didn't work.
Before I take it to a shop to have the codes pulled I am wondering if anyone has any ideas.
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I believe the ignition module on that car has two modules each firing two plugs. Check if the two that were burnt are on the same module. Possibly a bad module. I do not believe it is OBDII compliant so you may be able to flash the codes. You may need the service manual...

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Your '95 may actually be OBDII compliant. Check for a "D" shaped connector port beneath the dash under the steering column. It's covered with a removable black plastic cap.
As to the idling trouble: Check your EGR valve. (right side of the engine near the thermostat) If it's black plastic, it's an older model. The newer after-market versions are metal. A sticking EGR valve will cause rough idle on start-up and/or operation under load depending on which position the valve gets stuck *in*. 2.2l OHV engine re-circulates exhaust gasses into the combustion mix in order to keep the operating temperatures cooler. Also helps lower emissions.
B
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