part id please

hello all...i have a 91 chevy p/u with a 350 five speed. I am having some trouble identifying a certain is located on the driv
side of the block. when i am driving at normal operating temp..such as on the interstate at a modest 70 mph and suddenly give it the can hear the valves all chatter and a noicable decrease in power happens soon after. Also it triggers my check engine light. B4 i spend the money on OBD 1 tests i was wondering if anyone could give me their input. I have been told that this sensor is a type of heat sensor. When it goes causes this valve chatter to happen..similar to what the knock sensor does..only is triggered by heat. any hlp is greatly appreciated
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.