[67C10Step]

Best one I recall is my 1997 4Runner. It developed a tick that I thought was a valvetrain issue. To the point of taking it to the dealership and them telling me it did sound like valve train noise and what it would cost for them to repair. I decided to troubleshoot some more. Don't remember what they stated, but it was $$$.

I was out of town and my father in law happened to visit and my wife told him about it. He listened and told her it wasn't valve train, it was an electrical arc tick. He had been an electronics guy since the late 1960's in the Air Force. I started pulling spark plug boots and, sure enough, one of the screw on connections on one of the spark plugs had somehow came loose and was allowing the boot to jump a bit and arc. Total cost to repair was $0.0. Just a bit of time.