Hello, I would like to know how many miles you have on the vehicle.
There still a few possibilities of what could be causing the rough idle.
I have worked on Hyundais since 1998 and I have seen this problem caused by partially
fouled injector with a bad sray pattern, sticking valvesand EGR system, Tge ijector theory when car is cold start the engine needs a richer fuel mixture so the dribbling injector works fine but when the engine warms up it needs a very fine spray mist so a dribbling injector will caus the rough idle. Sticking valves happen usualy after the car heats up valve stem hangs in the guide causing a slow closure. The EGR valve can cause the same problem giving a rich mixture when cold it is ok but when hot runs realy rough.
I would like to know if you have had the car checked for any codes set by the onboard computer (ECM)Engine control module.I also would like to know if yes what the codes were.
Injector cleaner might help but that is a (might). Injector cleaner is an inexpensive tool but not always helpful if you have a badly fouled injector. I also would like you to make sure you hvae a good working PCV valve Positive Crackcase Ventalation Preferable a new one. the PCV valve is located on the valve cover and has a hose that has been know to suck in on itself creating a vacuum leak it should not be flat anywhere
I also wanted to know if the timing belt has been changed it was due at 60k
Hello again, Yes it could be fuel pressure related but I can tell you that motor is not very strong especialy with the a/c on
I would definatley check the green striped hose theory first. Don't forget get the car needs to be completely warmed up to where it is doing the rough idle and pull the green striped hose from the top of the throttle body. If the roughness clears up you will need to get a new EGR solinoid.
The reason I asked about the timing belt is because that motor is terrible about when the belt gets worn it will jump 1 tooth on a cam gear and cause rough idle but that idle is the way all the time.
Remember if this one breaks it will distroy that head.
Hello again I was wondering if you got anywhere on the problem yet.
I will check every day. Remember if you need anything just ask.