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I suspect 550s are on the large side for happy operation with a stock/Nistune RB20 ECU. The Hitachi ECU doesn't love short pulse width operation, and the RB20 doesn't need much fuel at idle. Big injectors can be unpleasant. This could be contributing. -
By joshuaho96 · Posted
Yeah, I still don't know why the idle speed control can't catch the falling RPMs. In the Consult logs I see the AAC duty cycle rising, but suddenly it goes lean and the engine stalls. Anyways, the relevance here is the DW 550cc injectors are probably the same. So if OP has similar issues I would be tempted to finger those injectors as problematic for whatever reason vs the ECU failing for some reason. -
Yeah, sort of blurring two different things together, aren't we? I just meant O2 feedback closed loop. I used to have a 0-1V LCD meter on my dash, wired directly to the O2 sensor signal. So you could easily see what it was doing. Normal running it would flick back and forth nicely. Slow down to an idle and it would keep flicking, as the ECU tried to servo to maintain stoich, but it would slow down as each swing happened until it would stay at one end of the scale. As I said above, the sensor heater is not enough to keep it hot enough when there is also little heat in the exhaust flow. Give it a blip and it would start swinging again, then peter out again. Meanwhile, idle speed control would run just fine, because unrelated.
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By joshuaho96 · Posted
It's not even O2 feedback, it's just simply when the ECU sees the closed TPS signal for whatever reason the idle will start steadily dropping until the engine dies. With the TPS adjusted to not trigger closed TPS it will idle at some ridiculously high RPM and something like 6 degrees of timing. In the absence of getting eyes on it personally and a lot of quality time doing diagnostics I couldn't tell you what the real problem was but it was interesting nonetheless
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