Lately I have been having an annoying problem with one of my distributor plugs that causes my engine to either die will driving or it won't let me start the engine. Here is a picture of the what plug I am talking about
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It's the darker colored plug that is more on the bottom side of the distributor.
Every so often it will just pop off and it's annoying because I have to get out, open the hood, and reattach it. Anyone know what causes this plug to just pop off like it does?