Engine overheats and idles rough when started warm

[silver8thcivicr18]

Over the past week my car has been acting funny,its a 2008 Civic ex. Ill drive it down the road just about a mile or so after i start it and the temp. gauge will be filled to the max but then it will drop a few bars,then gain some back, and repeat.I've drained all the coolant out and replaced it with the genuine honda one that im suppose to use and the temp guage read normal for about a day.I remember filling the reservoir to a little over minimum line.When i checked it today when i noticed the temp guage was full it was up to the cap.Also whenever i start my car after driving it for a few minutes it always idles very rough and sometimes stalls but after i rev it a little it seems to be fine but it has gotten gradually worse and the exaust fumes smell very sweet but there is no white smoke or leaks anywhere.Im thinking it might be the ECT sensors but i want to get some opinions before i spend the money on them becayse theyre fairy expensive.

[Zeuceone]

bad thermostat? cracked block like other r18's have had? got o the dealer?

[RJJensen]

dont mess..take it in...its under warranty

[lovecheese]

Call Honda and have them tow it in if I were you... just to be safe.

[silver8thcivicr18]

yeah thats probly what ill do.but now i gotta put all my stock parts back on lol.how much coolant should be in the radiator cuz i drained it and put a gallon in it cuz thats all i had but ive heard of some ppl filling it with 2