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Random Misfire

  • B744Driver
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24 Nov 2019 10:08 #35277 by B744Driver
Random Misfire was created by B744Driver
I’m new to the forum and am looking for some help.

2007 Kia Sportage 2.7L
Random misfire that seems to happen only at a stop or low speeds with the AC running. Its really random and doesn't happen every day. No DTCs.

I have captured the misfire on the secondary ignition side of two cylinders with the same result. The second half of the burn has a spike and then a large negative oscillation.

Based on what I see on secondary ignition I believed it to be a fuel issue so I have been looking at the injectors. I have been getting random short (1-3 extra pulses about 1Ms each) pulses when the AC turns on. This happens on at least three cylinders. Sometimes they overlap with the actual pulse and sometimes the current spikes as well. Is this normal?

I'm stumped at the moment as to where to turn to know for sure that its a ECM problem. Because the misfire is so random I have not yet captured the injector waveform during an actual misfire. Any thoughts or questions are appreciated.


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