Misfires — they’re our mortal enemy. Even when you’re not testing and tuning, errant misfires can be tricky to diagnose. First thing’s first, though: Which cylinder is missing? The old advice usually given is to pull spark plug wires until you find the cylinder which doesn’t further upset the bad idle, presumably meaning you’ve found the dead cylinder. While you will eventually find the dead cylinder, you’ll probably have a few defibrillations in the process if you’re doing this while the engine is running.
Skip that mess, and head to the exhaust! Each header primary is a breadcrumb that leads to a wealth of information about your engine’s current condition, and a quick inspection of the relative temperatures between each cylinder can spot a misbehaving hole. While we’re knocking this out with a $10 to $20 non-contact infrared thermometer (a must-have tool), you can accomplish the same basic task with gloves or a wet finger while quickly tapping each cylinder to feel for dead hole — don’t grab or hold any fleshy bits on there for long, just a quick peck will suffice. This super-quick spot check will buy time while you move onto the next step in diag.
Wrenchin’ Wednesday is a weekly garage-hackamajig, making wrenching great again with small tips that make working on your project easier, cheaper, and maybe even a bit faster. We’re probably not the first with any of these ideas, but you won’t be the last to know every Wednesday!
The other week we talked about using axle grease to keep fasteners in their place during assembly.
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