Okay guys, I have a 2004 Honda Accord and I've had this idle problem recently. At first I went right to the idle air control valve and replaced it. After that I continued to have problems so I started looking at vacuum lines. The line going to the PCV valve was collapsed so I replaced it along with a few other lines. Recently, I replaced the PCV valve, the EGR valve, the MAP sensor, the TPS sensor, and the air temp sensor. Every time I do the reset holding it at 3k RPM then letting it idle. Last night it idles fine and I took it for a ride, everything was good. After the ride I got home put it in park and the idle was going from 1000 to 2000 RPMs over and over. I keep checking the voltage on the TPS sensor and it's changing here and there so I readjusted and reset it. I don't know what else I can do anymore.

 

If your engine has over 80Kmiles and you have never done a valve adjustment, it is most likely in need of one.
If your engine has a mass air flow(MAF) meter, remove it and clean it with about half a can of MAF cleaner. Make sure to spray in every port. Reinstall.
Clean the air intake tract of any oil mist that occurs from the PCV system, remove the fresh air feed and clean it out as well.
Clean the TB throat and edge of the butterfly.
If your engine has over 80Kmiles, replace the spark plugs. Don't believe the million mile nonsense with plugs, they wear, they degrade. Replace them. Verify you have the correct ones, Calif and Fed have two different plugs. I prefer Denso Iridium TTs.
Verify the COP boots are not damaged or oil soaked.
Verify the spark plug tube wells are not fully of oil or leaking, this will degrade ignition performance.

 

The car has 280000 miles and I'm not sure if the valves have ever been adjusted. It does not have a mass air flow sensor but rather a map sensor and that has been replaced. I have replaced the coolant temp sensor the map sensor the throttle position sensor to EGR valve the air idle control valve new iridium spark plugs new throttle body gasket new air filter new vacuum lines the PCV valve, etc

Finally I bypassed they're idle control valve and replaced it again and it fixed the problem. Thank you for your help and your input