Not sure, but it does not move and there is no space to place a screwdriver blade between. Another symptom is that the exhaust when it does run gets abnormally hot...to the point of smoking. Could it be that this whole issue is being caused by a totally clogged catalytic converter? And if so, how the heck do I figure out which one of the four is bad? Thanks for all of you guys comments. I am no ready to give up on this yet...(getting close)