I have a 93 Integra with a dohc vtec when i revit up or driving and put it in gear and go at a low rpm and floor it while stiil low rpm it makes a loud ticking or knocking sound especially when i use reg unleaded gas. But when i use super unleaded gas you can barley hear it but its still there. So I inspected under the car only found a plug that wasn't pleged in and tryed to find a plug for it but couldn't find any around. What is this plug? it's located under the altinatior on the block behind the bottom pully. Can this be the problem?