Idle dips after a quick blip of the throttle. Timing is to blame possibly?

2002 Camaro SS a4. The car runs great, and fuel trims are nice. Has a larger camshaft (low 240's duration @ .050) a FAST intake w/ NW tb and is SD tuned.

after a quick rev if sitting still in park the rpms will come back down pretty fast and dip below the commanded idle rpm. It doesn't stall, but it is annoying. It will surge back up maybe 200 rpms over idle at times. On the log you can see that timing stays steady while this is happening at 18 degrees like set in the idle timing table. The idle stabilizes once adaptive spark kicks in....but why does it wait so long to take effect? This can go on for a second or two after before adaptive kicks in, but if the rpms are let down easy it will kick the adaptive in immediately.

I've played with the running air flow without much luck. RAF was set based on a cold start log of desired and then I've added a bit to it. I've played with the throttle follower values with no change or luck at all.... It seems the issue is the timing not correcting for the over/under speed of the rpm. I have the idle timing set to a value lower than the main table...why doesn't adaptive work immediately following a quick rev?

Mine does the same thing. Do you have a wide band? Its seems to be fuel related. When the throttle is slammed shut my wide band goes rich for a second as the car come back down to idle and just barley stalls. I was able to lean out the areas where this was happening and it helped. I watched the wide band and the LTFT histogram to see what was going on.

Yeah, I have a wideband in the car. I think going rich is an effect of the potential stall more so than the cause. I've tried leaning it out a bit with a hybrid open loop idle and although it may have been a bit better it would still do it.

As the car begins to stall it reads less vacuum (higher kpa) so maybe I should lean the area of the ve table out in the 80 to 90 kpa range and 400 to 800 columns. I think that may keep if from actually stalling, but it rarely stalls anyway...

Thanks

Try this tune

Attachment 40396

I'll give it a shot in the morning, thanks!

Quote:

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Originally Posted by Tick

Yeah, I have a wideband in the car. I think going rich is an effect of the potential stall more so than the cause. I've tried leaning it out a bit with a hybrid open loop idle and although it may have been a bit better it would still do it.

As the car begins to stall it reads less vacuum (higher kpa) so maybe I should lean the area of the ve table out in the 80 to 90 kpa range and 400 to 800 columns. I think that may keep if from actually stalling, but it rarely stalls anyway...

Thanks

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That is exactly what mine is doing. Less vacuum higher KPA, as the car comes back down to idle. It hits the 75, 80, 90 KPA cells then jumps over to the 400 RPM column. My car idles at 850 RPM at 65-70 KPA.

Mine turned out to be the throttle follower. I took the decays to 3 across the board and zeroed out the delay. Now the IAC closes really fast when the throttle is slammed shut from a rev. For some reason my car seems to only like about 17 degrees of timing at idle. Any higher and it starts to stall again after a quick rev, and my IAC counts start to get to low at hot idle.