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1998 Civic LX idles kinda hard and low at around or below 500 rpm. It feels like it's gonna die but it never does, sometimes I used to have to rev the engine for it to gain the rpms and stay on. It only happens when the car is running hot. It starts up perfectly fine on cold start. I was just wondering what the issue could be, I've been told it could be the idle air control valve and that I just need to screw it down because it could be letting in too much or too less air. If anyone thinks that is the issue, what would be the best way to go about that? I think I can rule out a vacuum leak because there is no high pitch noise and it doesn't seem like thats the issue. Any suggestions would be helpful, TIA.