[HeWhoKillz]

So, some are probably used to me posting about my 91 corolla with a bubbling coolant issue. I finally got a few minutes to go mess with the car and I decided to start the car and pulled off each spark plug wire while it ran. The first three it was worse as it ran but the 4th one it sounded the same since the car has a sputter with it. So can I assume this is the culprit cylinder? I switched the 3rd and 4th spark plugs and wires just to see if the 4th one was bad and it ran the same. I also found I have a bolt that I'm not sure if it broke off or is missing but its on the exhuast manifold. There is a little exposed space and pushing the exhuast manifold up against the engine makes the engine quieter, obviously. But I was thinking, with a small gap between the engine and exhuast manifold, can that cause bubbling in the coolant? Air has to be getting in somewhere. What other steps should I take to deal with the 4th cylinder?