Obviously it is the engine... just what in the engine may need more discussion. Depending on the condition of the exterior and the interior, you would have to decide on the proper course of action. Putting in a lower mileage salvaged engine would probably gain you another 100,000 to 200,000 miles so it is a cheap alternative.Let's see if we can narrow down the possibilities... If the engine starts easily like most Hondas, it means you still have good compression which would tend to rule out the piston rings. Leaking valves tend to reduce compression also and make for harder starts and poor performance. However, there are valve seals attached to each valve that keep oil in the cylinder head from getting down into the combustion chambers when the intake valves are open. Similar seals are on the exhaust valves but leakage there ends up in the exhaust manifold where it is still hot enough to burn and produce smoke but shows little affect on performance.Fixing piston rings is basically an engine overhaul. If your car is approaching 300,000 like my '90 Prelude, fixing just the valve seals is cost prohibitive (unless you can do it yourself) when it is likely something else is on it's way out. Even Honda's don't last forever without assistance!Valve seals can be replaced without a major overhaul... have a mechanic do a compression check of each cylinder that will tell you a lot. Getting to the valve stems in a Honda with a 4 cylinder engine is not much of a problem either. They will provide a quote for replacing valve stem seals.Get the Helm service manual for your Hondas... it's worth it's weight in gold!
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