Abstract
In order to understand and resolve the exhaust valve carbon sticking problem, the engine parameters effective on the phenomenon are shown by bench tests. Based on the results, a new test code which can evaluate the exhaust valve sticking has been developed. And by using the test code, the effects of engine hardware, gasoline properties, and warm-up enrichment are shown. Finally, the detailed mechanism of the exhaust valve carbon sticking is clarified and solution to it is proposed.