I have a honda insight 2010 with 250,000 miles on it. I have done a lot of maintenance on it a tune-up and regular oil changed and transmission fluid changes. The engine is dry as a bone underneath. I…

trilex

I have a honda insight 2010 with 250,000 miles on it. I have done a lot of maintenance on it a tune-up and regular oil changed and transmission fluid changes. The engine is dry as a bone underneath. I know I need to do a coolant flush on it. The engine has a rough idle when I'm at a stop sign. I have changed the pcv valve and even did a oil treatment and used OEM oil. There are no lights on the dash do you have any recommendations to get rid of the rough idle or to think of service as this is a high mileage vehicle?