The　effects　of　multiple　operating　parameters　(including　speed,　valve　timing,　lambda,　manifold　absolute　pressure,　spark　timing,　and　hydrogen　injection　timing)　on　the　coefficient　of　variation　of　indicated　mean　effective　pressure　(CoVIMEP)　of　a　hydrogen-blended　ammonia　engine　have　not　been　adequately　evaluated,　which　motivates　this　study.　Specifically,　CoVIMEP　is　decreased　from　exceeding　2.4　%　to　approximately　0.7　%　when　the　speed　increases　from　1300　rpm　to　2000　rpm.　Optimizing　valve　timing　keeps　CoVIMEP　below　0.8　%　by　improving　the　airflow　exchange　process,　and　the　engine　tends　to　realize　lower　CoVIMEP　at　close　stoichiometric　ratio　conditions　and　low　pumping　loss.　Furthermore,　adjusting　spark　timing　affects　CoVIMEP　by　varying　the　ignition　process＇s　stability,　with　a　combustion　center　of　gravity　around　9　degrees　CA　ATDC　being　suggested.　The　hydrogen　direct-injection　timing　influences　the　combustion　process＇s　instability　by　varying　the　mixture　concentration　gradient,　and　the　late　injection　strategy　allows　the　engine　to　achieve　a　CoVIMEP　of　less　than　0.9　%.