We hear these questions all the time. Mechanics are just ripping you off right?
The short answer: Testing saves you money and from receiving a headache.
The long answer: We take immense pride in the work we do. The only way to properly fix a vehicle is to properly determine what is causing the malfunction, no guesswork. Bringing it back 3-4 times paying for separate repairs that may or may not fix the concern you brought it in for is unacceptable. We spend thousands upon thousands of dollars on equipment, software, and training to make sure that when you leave, you leave in a better condition than when you came.
The photo shows a truck with a misfire that was brought to us after somebody else replaced hundreds on parts without fixing the issue. We scoped the injector and found it had no mechanical movement inside within 1 hour. Fixed the first time with a happy customer!