Need some help troubleshooting idle stability when warm - Miata Turbo Forum - Boost cars, acquire cats.

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Old 07-19-2016, 06:53 PM   #1
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Default Need some help troubleshooting idle stability when warm

I have an MS3x on a '99 with a Kenne Bell SC, I built and installed. The car appears to work well now that I know how to tune the idle valve, fuel, and idle up, AC, etc. It starts up within 4 seconds when it has sat for a while and 1.5 to 2 seconds when warm. The problem I have is an idle that seems to fluctuate when warmed up (sitting while idling).

I tuned the Idle VE table in every cell using the Idle valve opening steps and idle target, while NA. The transition from cell to cell is smooth and the car stays in the correct cell when the map is constant. I have also filled in the cells in the Fuel VE table with appropriate values that match the AFR target and roll into the IdleVE cell values. With these settings, the car seems very stable at idle and the transition is smooth. The timing is also stable around these cells.

However, when warm, the car will begin to oscillate in AFRs (13.1-15.1) and therefore RPM (1000-1200). If I didn't have an AFR meter, I probably wouldn't notice as much. However, I want a rock solid idle. I understand AFR at idle changes with temperature and during warm up, but it shouldn't oscillate with a steady fuel value. I don't have any indication of the AFRs not being stable under load. However, I feel like I experienced a misfire at around 2500rpm once, which lead me down this train of thought.

Does anyone have a suggestion of what it could be? I am thinking a slight misfire, but the plugs aren't old and the wires are new-ish. Coil (I'm using stock)? Anything I can check for in my logs? I will upload them tonight.
Attached Files
File Type: msl 2016-07-17_12_modified.msl (1.67 MB, 5 views)
File Type: msq CurrentTune.msq (237.7 KB, 3 views)

Last edited by 3rdCarMX5; 07-20-2016 at 03:14 AM.
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Old 07-20-2016, 12:29 AM   #2
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Sounds like your already running closed loop idle. Are you using adaptive timing? It worked miracles in my NA and really solidified the already pretty stable idle in my MSM.

Do you have a log of the oscillation?
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Old 07-20-2016, 03:15 AM   #3
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I uploaded a log, I think the oscillation is captured at the very beginning.
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