i have just got an 1998 2.0 16v vectra engine code x20xev it starts no problem no knocks or bangs the engine runs smooth until it get to about 90 on the temp on dash then the engine seems to judder it is using coolant but no white smoke out the back but i have been told it is running rich but the temp go's no higher than that anyone got any ideas?

memphis200760, July 2010