This part of the cycle is when the mixture of air and fuel ignites and how the flame front spreads in the cylinder.
Being able to use a scope allows you to make a more accurate diagnosis faster. It is a tool that can prevent that second call to a customer advising them the initial estimate did not work. It can also be a triage tool that can save you from having to remove plugs to perform a compression test or give additional evidence if a misfire is electrical or mechanical.
Just this summer, I experienced a situation in which the fuel pump had been replaced four different times on a single vehicle with no result because the various repair shops attempting to repair the vehicle didn’t understand how to diagnose a pulse-modulated fuel delivery system. Here are five things you should know about diagnosing them.