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Thread: Where's a good starting point for cold idle surging

  1. #1
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    Working on my cold idle surging

    I'm working on a friend's Trans Am. Once the car is warmed up it runs fine. But, until it warms up it hunts for idle continuously. It doesn't cut off but it dips and surges significantly.

    It's got a Fast 90/90 intake/throttlebody.
    The cam is a Torquer V2 232/234 .595"/.598".
    The heads are Patriot 64cc.

    Here's my tune and log from this morning.

    Tune, log and config are in the last post.
    Last edited by 99LS1SS; 02-16-2012 at 09:39 PM.
    2016 GMC Sierra 1500 6.2L

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    The wideband isn't hooked up yet on my log. That's why it's reading what it's reading.
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    I might have figured it out. I reduced the values of the Open Loop F/A vs. Coolant Temp vs. MAP in the kPa and RPM area that the idle uses. It seems to have helped some. I'll adjust them a little more to see if that was the fix.
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    once your idle ve and maf trims are in spec, you will need to change your BRAF (base running airflow)

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    I've changed all of those. It idles perfectly once warm. Only in open loop does it surge.
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    Tuner smokestack's Avatar
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    Quote Originally Posted by HoP View Post
    once your idle ve and maf trims are in spec, you will need to change your BRAF (base running airflow)

  7. #7
    Senior Tuner Ben Charles's Avatar
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    once your idle ve and maf trims are in spec, you will need to change your BRAF (base running airflow)
    This is an incorrect statement

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  8. #8
    Senior Tuner edcmat-l1's Avatar
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    Quote Originally Posted by 99LS1SS View Post
    I've changed all of those. It idles perfectly once warm. Only in open loop does it surge.
    Open loop EQ table. Adjust it. Lower it significantly in the colder temp ranges. I always set the 140 F and up columns to 1.00.

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  9. #9
    Senior Tuner edcmat-l1's Avatar
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    Quote Originally Posted by Ben Charles View Post
    This is an incorrect statement
    Ben, wait til you see what I been workin on. I'm gonna post a video of it in the next week or so. Give ya a hint. You will definitely like it!!

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  10. #10
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    Quote Originally Posted by edcmat-l1 View Post
    Open loop EQ table. Adjust it. Lower it significantly in the colder temp ranges. I always set the 140 F and up columns to 1.00.
    Thank you for the confirmation. I lowered all of those cells and it helped dramatically.
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  11. #11
    Advanced Tuner gn2beatu's Avatar
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    Your also running over 20 degrees of timing. Try lowering the timing, and I bet that fixes the rest of the hunting. Mine likes 14 degrees and it doesnt surge at all. Most of the newer cars I have worked on like somewhere between 14-16 degrees.
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  12. #12
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    Quote Originally Posted by gn2beatu View Post
    Your also running over 20 degrees of timing. Try lowering the timing, and I bet that fixes the rest of the hunting. Mine likes 14 degrees and it doesnt surge at all. Most of the newer cars I have worked on like somewhere between 14-16 degrees.
    The timing has nothing to do with it. With the cam he has, it will idle like crap at 14-16 degrees of timing. I would be running every bit of 20 degrees in it, maybe slightly more.

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    I dropped the Open Loop EQ cells down and it surges MUCH less than it did. It now dies on the first startup but keeps running on the second. Do I need to up the Open Loop EQ cells in the 34 degree range or is it something else that's causing it?
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  14. #14
    Senior Tuner edcmat-l1's Avatar
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    Quote Originally Posted by 99LS1SS View Post
    I dropped the Open Loop EQ cells down and it surges MUCH less than it did. It now dies on the first startup but keeps running on the second. Do I need to up the Open Loop EQ cells in the 34 degree range or is it something else that's causing it?
    Hard to say without a data log. could be in the base running idle airflow. Could add back 3% to the OLEQ table and see how that does.

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    I have a log of this morning's cold start but it's at the house. I'll see if I can get it at lunch and post it.
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  16. #16
    Senior Tuner Ben Charles's Avatar
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    Ben, wait til you see what I been workin on. I'm gonna post a video of it in the next week or so. Give ya a hint. You will definitely like it!!
    I Like the sound of this , does it have anything to do with the 4L80E TCC???

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  17. #17
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    Here's this morning's log. You can see it cut off and then stay running.
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    I'm whittling away at the cold start. I only had one small section of hunting this morning. I think tomorrow or the next day it should be dialed in.

    I basically got tired of hacking the idle tables to get my idle stable and I started to focus on idle airflow and idle timing. I was altering other tables to force those two tables to stay in line. I realize that was a shitty way to tune so I set all my "helper" tables back to stock and only adjusted idle rpm and idle airflow until it would idle smoothly where I wanted it do. As it turns out the helper tables are MUCH less needed if you start off with a good solid idle.

    I posted what I did in hopes that my epiphany helps someone else.

    I had a tiny bit of bucking when I was at 45 mph and ~1500 RPMs. I've lowered and smoothed the timing in the idle tables as well as HO timing tables. That should address that issue.
    Last edited by 99LS1SS; 02-10-2012 at 07:49 AM.
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  19. #19
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    I have made some improvements in the manners of the car. I'm still getting beat down by the cold startup. I'm out right now but I will post an idle log with my current tune as soon as I get home.

    Can anyone tell me the "usual" causes of cold start surging? Once it is warm it is fine.
    2016 GMC Sierra 1500 6.2L

  20. #20
    Senior Tuner Ben Charles's Avatar
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    Got to have Fuel, Air, Spark correct, probably a mixture of Air and fuel. What does your OFLA table look like, did you leave it stock?

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