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Chased a ghost misfire for 11 hours, turned out to be a cracked flexplate
Tbh I thought I was losing my mind. 2015 Cummins in a Ram 3500, customer said it had a "skip" under load. Compression tested fine, injectors swapped, fuel pressure checked out, even pulled the valve cover to watch the rockers. Still misfiring. On hour 11 I had the truck on the hoist for something else and noticed a hairline crack running through the flexplate near the crank bolt. Whole thing was flexing just enough to make the crank sensor read erratically. Replaced it and the truck ran smooth. Anyone else ever waste a full day on a sensor reading that was really a mechanical issue? How do you catch that faster next time?
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sandra_moore308d ago
A cracked flexplate is not a "misfire" in the normal sense, so I would not beat myself up over chasing it for a day. Yeah it makes the crank sensor act up, but that fault path is rare enough that most guys would swap sensors and injectors first too. Calling it a "waste" is a stretch when the diagnosis was right in the end and the truck got fixed. This is just how oddball failures go, you rule out the cheap stuff before you start pulling transmissions. The only faster catch would be a scope on the crank signal, and even that can look like a sensor fault. Some jobs just eat a day and that is part of the deal.
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