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05 Infinity G35 Random Misfire
by 1986chevyman on Feb 05 2019, 5:56 PMElite Tech
Had this G35 come in that would barely run and was back firing thru the intake manifold. Customer stated that his sons had replaced the valve cover gaskets and also installed new spark plugs. He also said that a friend had scanned it and thought it was a vacuum leak. My gut told me that this felt like when you installed plug wires in the wrong order on an older distributor model car. So I printed out the wiring diagram for the ignition coils and checked the connectors. Sure enough cylinders # 4 and #6 were hooked to the wrong connectors. I hooked the connectors on#4 and #6 to the right coils and reinstalled the air boot and fired up the engine. No more popping thru the intake, but the engine felt like it had a misfire. Unfortunately this model does not have misfire data PIDS. So I went to Global , and looked at Mode 6 data no misfires showing up. So I went back Infinity diagnostics on my Autel Maxisys Elite and found a power balance test. I found when killing cylinder number 2, there was no RPM drop. So next I pulled cylinder #2 ignition coil and there it was. I could see a burn mark on cylinder #2 ignition coil shaft where the spark was arcing to ground. Replaced the bad coil and test drove. The vehicle was fixed.
So the moral of the story, is to get as much information as possible (clues) and if your gut tells you something, check it out.
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