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Missfire LS Engine
Posted to Technical Tips Forum on 6/12/2019 5 Replies

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 good and from #8 was defective. Replaced #8 coil and cured problem. I cannot begin to explain why #8 coil caused #7 to misfire nor can I explain why moving it to #4 caused #3 to also misfire. I just know it did so if you run into something like this my experience may save you a lot of time.

Tim Kuehl
Owner/Technician
Old Geezer's Garage
Montgomery, Texas, USA

5 Replies Received (View Replies)

 

car Vehicle Data

2004 GMC Yukon SLE 4.8L

Engine4.8 L
Trans4-speed Automatic (Electronic)

car Vehicle Data

2004 GMC Yukon SLE 4.8L

Engine4.8 L
Trans4-speed Automatic (Electronic)