Try to go over there sometime and open the coolant reservoir cap after it has been sitting overnight. There should be no pressure. Drive the car on the freeway for about 10 miles and then pull off the freeway and let the car idle. It should be pretty doggone smooth but will not be as smooth as the Honda when it was healthy. Start the car cold sometime and make sure it starts without having to give it any fuel and it idles out smooth immediately. It could require a valve adj if it does not do all of the above BUT if there is pressure in the reservoir when it is cold then there are some head/head gasket issues.

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Jim