Another Misfire Mystery Solved


More fun with misfires! Last month, it was an early-OBDII Honda misfire. This month, it’s a domestic. Tim from Texas provides a very useful, quick tip for anyone trying to diagnose a GM LS engine misfire and seeing a strange misfire pattern. In his diagnostic routine, we swapped the coils to see if the misfire followed. It did, but he got more than he bargained for. This is another great example of the immensely helpful information shared daily by the community at Check out his post to learn this great tip.

Misfire LS Engine

Misfire on cylinders 7 and 8 with cylinder 8 having a larger percentage of misfires. In determining cause I moved the coils to different cylinders; coil from 7 went to 5 and coil from 8 went to 4. New misfire data showed cylinders 3 and 4 misfire. Conclusion: Coil from #7 was…Read More

Extra note from a comment posted on this thread:
It was stated that this is referred to as a sympathetic misfire caused the problem cylinder. The problem cylinder misfires, which slows the crank enough that it shows up as a misfire on the next cylinder. In this case, where the firing order is 18726543, cylinders 7 and 3 exhibited this sympathetic misfire. But, 8 was the source of the problem, which manifested as 4 being the problem when the bad coil was moved from 8 to 4.

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