I went from a 3200 stall to a custom 4800 and some even bigger heads. After retuning it idles steady and drives great except for one little thing. When idling in park or driving slow if I blip the throttle to 2500-3000 rpms the idle dips 350-400 rpms and then recovers. My question is which way and in what area do I need to adjust the throttle follower to get rid of this?
Any input will be greatly appreciated.
It is a 2004 LS1 with a fast 102, 102 tb cable throttle body with 100 mm maf.
Last edited by sunny; 03-05-2013 at 04:10 PM.
If it comes down to fast (which sounds like it is) you need to reduce the numbers to slow the decel of the throttle. Adding airflow down low to the TF airflow will help catch it as well.
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Thank you Ben that is exactly what it is doing.
Last edited by sunny; 02-23-2013 at 08:15 AM.
I rarely find it necessary to change factory setting on TF air; I would focus on idle air in park value in typical engine operating temperature range and the values for idle air limits listed on the "idle" "airflow" tab. It is also possible your throttle blade screw just needs adjusting so the blade is open a slight bit more at idle, however if doing this results in a fast idle then this was not the case and it should be returned to previous setting.
The values in the IAC step table can impact this too however this would typically also cause problems with cold starts if these values were too low in the first part of the table that is active when you are at idle in park at normal engine operating temperatures (probably between 20 and 45, but is unique to each vehicle/motor).
If you insist it is the throttle follower you can try different multiplier values for the lower RPM cells in the corresponding table.
This is simply a trial and error process and is all part of "learning" to tune.
Thanks for your input James.
The cold start is great and I have the idle air perfect in park and drive. The idle is perfect at 900 rpm and drives great. It only dips after quick revving as stated above.
I had considered opening the throttle blade a little more if the TF adjustment doesn’t work.
I agree it is trial and error I spent half the day yesterday getting it to where it is now. LOL
Last edited by sunny; 02-23-2013 at 09:35 AM.
Any luck yet?
I’m getting there I have the in park issues fixed. When the weather clears I’m gong to work on the last small problem. If I’m in gear coasting between 10-15 mph and give it 6% throttle to 2000 rpms and let off quickly the idle dips to 640 rpms. Then it starts oscillating up to 1800 rpms and back down to 640 six times then recovers.
Larger throttle inputs and drops produce no problems.
I have gotten it to this point by slightly opening the idle screw and resetting 0, greatly reducing timing, and increasing throttle follower delay.
My plan for the effected area is to further smooth timing, look at the IAC steps and more adjustment to throttle follower.
Thanks again
Last edited by sunny; 02-26-2013 at 09:14 AM.
I got this thing to idle at 1000 rpm without occasionally stalling by running OL and some heavy adjustments to throttle cracker, throttle follower, and TF delay.
I think that my small diameter torque converter, big heads, 346ci and the fact that it is cable driven causes the need for the higher idle speed.
If I had it to do over again I would have used a 90mm TB.
Your opinions are welcome.
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