4 year old spark plugs? kung iridium plugs pwede pa sigurong umabot ng ganun but I assume hindi iridium ang nakalagay sa inyo.
anyway, I suspect your distributor is damaged. here is my take..
1. change the whole distributor
2. change the high tension wires
3. change the plugs pleeeaase
no wonder bakit erratic ang idling niyo sir, your plugs might be full of deposits at hindi na maka-emit ng spark, in short pangit combustion, mahirap mag-start.
just start here sir, if you still stalled, you can post here again, I will try to diagnose your problems based on your post.
Maganda po burn ng spark plug niya, bosch na platinum sya, saka quick start po sya before sya nagkaproblema, napalitan na namin distributor nya ng surplus, so far ok na sya ngayon