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Old 08-20-2014, 12:34 AM   #1
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Default Not sure if misfiring under load or something else...

So initially, I had an issue where the car would misfire around 6k while on the dyno.

I've since added two capacitors to the positive and ground of the COPS (30uf total) and gapped the plugs wider from 0.025" to 0.040". I ensured that the cap was correct on the Crank Position Sensor which is being used to run batch fire/injection. Everything seems to be running a bit more smoothly, but I hadn't been able to get it back on the dyno yet.

Tonight I encountered a new...symptom around 4.5k at full tilt. It feels like boost/spark cut but it I don't know what else to look at.
On the log, at SecL = 651 is where things start to go dicey. It is outlined in the image below. It doesn't hold pressure and bogs. It feels a bit dependent on load; under partial throttle, it response a bit better, but 'misfire' sensation is still present.





The only thing I did in the last two days was install a FM butterfly brace, new driveshaft and changed the engine/trans oil. Nothing related to the tune. I'm at a loss and well in above my head now. Any help is appreciated.
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Last edited by psyber_0ptix; 08-20-2014 at 01:47 AM.
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Old 08-20-2014, 12:12 PM   #2
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It is running a bit rich in that spot, but I don't see any other potential issues.
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Old 08-20-2014, 01:41 PM   #3
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It got me wondering, while folks are able to run 0.040" gap with cops, I bet running this rich still causes spark blowout. I replaced the plugs to the out - of - box 0.036" and also re-flashed to the latest firmware out of desperation. Because I had readjusted the crank position sensor, I wanted to double check the timing and found I had to adjust the #1 tooth angle by 0.5 degrees. No big deal, but are these sync errors acceptable? It doesn't lose sync, just curious.


To make a long story long... It seems to be doing a lot better for now. I just hope that 6k+ stutter went away so it can make its way to the dyno again. For now I'll have to redo some of the idle settings but I'll consider this case closed for now. I'd like to know what changed for this to occur randomly. Maybe fouling plugs.
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Old 08-20-2014, 05:12 PM   #4
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I don't see any sync errors in the log.
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Old 08-20-2014, 05:50 PM   #5
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My mistake, I meant timing error
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Old 08-21-2014, 11:53 AM   #6
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The timing error logs are sampled too slowly to be particularly useful. I wouldn't worry about the readings you have.
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