Stumbling upon clutch in on coast down

Been a while since I've been on but i have an application thats kicking my butt! Its a 2000 Trans Am, M6 with the following mods...

408CI Ported 243 Heads
FAST102/102 setup
244/254 .630 113lsa cam
11.5:1 CR
Speed Density

Car runs great, idles at 1050, drives good with very little surge for the size cam it is. My throttle cracker works perfect holds me at 1250rpm till i come to a full stop. However where it seems to get angry is clutch in on coast down, it will dip and surge around. Soon as i come to a stop the idle PI will catch it and its fine. First thing i did was add 3g/s of air to the b4310 table, this seemed to have no effect, i cranked it up to 20g/s to see if it worked and nothing. So it seems like b4310 is doing nothing, which is a shame because it would by my fix. I even went as far as trying to let the idle control run it at all times by zeroing out the 400rpm error in the learning table so it wouldn't correct on coast down. This worked but soon as i get within that 400rpm window of idle it will correct the iac down to 0 and it will stumble. I can post up the tune and logs if need be. Also i did do the RAFIG process and desired airflow is correct. VE table is also dialed and its idling comfortably at 14.5:1 in OL. What i really need is the throttle cracker to just stay active no matter clutch in or out until it comes down to 3mph. If i could get it to do that it would run PERFECT. By the way the car seemed to run perfectly fine until the FAST 102 and 102 TB went on it then all this junk started happening. I checked for any vac leaks and didn't find anything.



Any input would be appreciated.

Thanks!! :cheers:

Quote:

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Originally Posted by quik95lt1

By the way the car seemed to run perfectly fine until the FAST 102 and 102 TB went on it then all this junk started happening.

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You're not the first person this has ever happened to. :laugh:

What is spark doing...?

Post logs and tune.

Is FAST102 leaking internally or externally...?

Check that TB IAC passage is not blocked.

I got it solved, I wound up setting the throttle cracker to 2g/s across the board which gave me a 1250rpm idle, then I zero'd out the decay so it couldn't decay back down on the roll regardless of clutch in or out. I set the disable mph to 2 so when I come to a stop it decays out and goes back to using the learned idle. Worked great!

That's not how I would have fixed it, but a fix is a fix. The main thing is that you found a solution that works for you... Well done. :cheers:

Good job :cheers:

( and check the FAST102 for leaks anyway )

Which TB are you using...?