As vehicular technology advances, misfires are becoming more common and not less. In an age when computers were supposed to make our lives easier, they occasionally cause headaches for even the most talented technicians and shops. Instead of narrowing down the possibility of an engine misfire, the reliance upon vehicle-specific components and modules has made misfires (and the mechanical sequence leading up to them) more problematic than ever.
As John Forro at Automotive Video Innovations notes in one of his diagnostic classes, “there is no golden ticket to follow” to discover the cause of a misfire; rather, it’s best to focus on the path of least resistance in discovering its source.
Identifying the cause of a misfire is less like diagnosing a known issue and more like some sort of digital automotive forensics. The result of the crime—if you will—is clear, but the how’s and why’s leading up to it are murky. So pull your collar close and prepare to get your hands dirty, gumshoe—it’s time to uncover the sordid truth about misfires.
As Long As There Are Cars, There Will Be Misfires
“Misfires are a never-ending headache,” says Tom Rayk, diesel program coordinator at Automotive Video Innovations.
“You have to use ALL the information available to you to properly diagnose and solve the problem. Drivability suffers as misfires proliferate and the car can become compromised and create dangerous problems.”
Rayk says that misfires can be more like misphantoms than anything; they tend to come and go seemingly at will. “Some misfires are caused by a faulty wire connection or a pothole that knocked a module loose,” he says, “and usually the customer isn’t wrong; they know their car, even if they can’t identify the problem or why it’s misfiring.”
The critical thing about training how to properly diagnose misfires is that properly identifying the root cause is more a process of elimination than anything else; similar to how astronomers identify black holes by the sheer absence of light and odd gravitational phenomenons, misfires present a similar dilemma—they’re defined and isolated more for what they’re not than for what they are.
“They’re difficult to fix,” he adds, “and you have to use all your advanced diagnostic training. You have to take all the clues, do all the testing, and narrow down your choices,” he says, “and you have to eliminate this suspect wire or that unimportant module, and once you’re able to set some suspects aside, the path is a little more clear.”
Automotive forensics indeed. To learn more about how The Group Training Academy and AVI can help your shop more accurately diagnose and fix misfires, please click here.
A Logical Approach to Misfires
Though it’s easy to think of misfires as just another problem to fix, simplifying the difficulty of properly diagnosing a misfire can lead to costly comebacks and unhappy customers. As John Forro notes below (and as in many endeavors), process is king and will help clear the path forward.
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“If we apply a similar process to misfires as we do to other types of diagnostic scenarios, we will surely improve our diagnostic skill set. It is crucial to understand how the system works, to acquire the necessary data to determine where the problem may lie, and then to use a commonsense approach using diagnostic tools to determine the root cause.
Remember, the actual diagnostic tests you choose will often differ from one vehicle to the next. There’s no silver bullet—rather, proper assessment and a deliberate process of elimination will reveal the path of least resistance in diagnosing a misfire.”
