Surge-stall when cold
04-07-2008, 11:37 PM
#1
Surge-stall when cold Hi,
My car has an A4 trans. and a 224/230 cam. I just had it tuned recently. It seems to run real nicely, but, when the engine is the least bit cold, it will surge and stall when it's trying to idle. When it's warmed up, it idles pretty well. My buddy showed me the tables, and the in-gear idle speed is set at 875 rpm from 68-degrees through 111-degrees F, where it steps down to 825 @ 133-degrees, down to 735 @ 154-degrees, and 725 @ 177-degrees and hotter. Does that seem about right for what other people have? Is there anything else that might cause this?
Thanks!
My car has an A4 trans. and a 224/230 cam. I just had it tuned recently. It seems to run real nicely, but, when the engine is the least bit cold, it will surge and stall when it's trying to idle. When it's warmed up, it idles pretty well. My buddy showed me the tables, and the in-gear idle speed is set at 875 rpm from 68-degrees through 111-degrees F, where it steps down to 825 @ 133-degrees, down to 735 @ 154-degrees, and 725 @ 177-degrees and hotter. Does that seem about right for what other people have? Is there anything else that might cause this?
Thanks!
Last edited by 30th droptop; 04-08-2008 at 01:47 AM.
04-08-2008, 10:27 PM
#3
TECH Junkie
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try upping the idle, and also do you have a way to log the idle parameters? like hptuners? I'f I had to guess your adaptive spark at idle is off as well as your VE and RAF table with VE being the most important one to look at.
04-09-2008, 11:26 PM
#4
I had my buddy look at the "Idle Adaptive Spark Control" tables in HP Tuners. In the "Overspeed" table, it lists -1 @25 rpm, -2 @50 rpm, -3 @ 75 rpm, -4 @ 100 rpm, -5 @ 150 rpm, -6 @ 200 rpm and -8 @ 250 rpm and faster. The "Underspeed" table lists 0 for everything except -175 rpm, which lists 4.
I will see if we can up the idle speed a bit at lower temps. to see if that helps.
Thanks!
I will see if we can up the idle speed a bit at lower temps. to see if that helps.
Thanks!
05-02-2008, 12:56 PM
#5
Thanks, Mike K.
The cold start-up and idle are much better now. I used Nogo's default idle suggestions one at a time, saving VE for last. The VE is what really made the difference, like you said. When I used Nogo's suggestion of multiplying the 400 rpm column by .6, the 800 by .8 and the 1200 by .9, it tended to load up and stumble on acceleration when cold. So I put the values halfway between his suggestions and the stock values. It seems to work pretty well.
Being new to EFI tuning, I don't really understand much, so forgive a dumb question, but what am I actually changing when I modify the VE table? It seems to get effectively richer with smaller numbers. I just bought an Innovate wide-band AFR unit and will check the actual AFR at idle to see what I've got. This is all new territory for me - my experience is almost all on carbureted cars . . .
The cold start-up and idle are much better now. I used Nogo's default idle suggestions one at a time, saving VE for last. The VE is what really made the difference, like you said. When I used Nogo's suggestion of multiplying the 400 rpm column by .6, the 800 by .8 and the 1200 by .9, it tended to load up and stumble on acceleration when cold. So I put the values halfway between his suggestions and the stock values. It seems to work pretty well.
Being new to EFI tuning, I don't really understand much, so forgive a dumb question, but what am I actually changing when I modify the VE table? It seems to get effectively richer with smaller numbers. I just bought an Innovate wide-band AFR unit and will check the actual AFR at idle to see what I've got. This is all new territory for me - my experience is almost all on carbureted cars . . .
