need suggestions for tune problem

[brettmc]

96 lt1 t56 AI heads/cam. Using JET DST to tune with.

I have a problem with the IAC value going to zero coming to a stop. Of course at that point I'm still rolling, maybe 5-10 mph, and it wants to die. So what I have to do is heel and toe the throttle with the brake foot to keep it from dying. Usually a couple of quick stabs at the throttle and it'll idle fine at that stop. Then at the next stop the same thing. This is the only idle drivability issue I have.

I can't figure out what needs to be changed in the idle constants and tables.

I can provide any type of data needed from logs to sections of the tune to the entire tune. Whaddya need?

[blkchevyz]

whats your iac at when you are just idleing and warm?

[brettmc]

if memory from last summer serves, around 40 counts.

[tleed]

Have you tried to open up the throttle blades a little

[brettmc]

i have not. it idles great if the iac doesnt go to zero. i even put a new iac on it towards the end of last season....around oct.

[brettmc]

to clarify, me being a dumbass tuner caused this. instead of changing one thing at a time, I changed several. then several more. then this problem started. yeah, yeah, i know now....

[blkchevyz]

do you have any iat to mph tabs? also did you change anything with the idle telling it to idle lower while moving?

i know tuner cats has a throttle follower iac vs mph.

[brettmc]

yes, there is a table like that. i'll post it up when i get home.

[brettmc]

throttle follower iac vs mph
mph steps
0 30
4 30
8 30
12 30
16 30
20 1
24 1
28 5
32 5
36 5
40 5
44 5
48 5
52 5
56 5
60 5
64 5

[brettmc]

tps iac offset vs rpm

this table is all zeros

[bigtoyz]

Here is my table for the Throttle follower IAC vs. MPH

0 2
4 4
8 8
12 10
16 10
20 10
24 10
28 10
32 10
36 10
40 10
44 10
48 10
52 10
56 10
60 10
64 10

Edit: my counts are at 40 and idles pretty good and returns to idle pretty quick also

[brettmc]

does this table add the iac counts at that mph or subtract or is this the actual count value at that mph?

[blkchevyz]

do you have the stock tune or the one you had before modifiing it?


i'm running an obd1 but my throttle follower iac offset is
3
4
8
12
16
20
20
20
20
20
20
20
20
20
20
20
20

this was on a large head/cam car and idled great.

[brettmc]

do the offset tables add or subtract?

thanks for the table hints. i'm going to try some of these after work today.

[blkchevyz]

i would think it would open the iac valve more with the higher number, since most cars idle high till you come to a complete stop then drop down.
but that way you would think you wouldnt get the idle to go down... but who know could be pushing it past the limit or just cant keep up, or i could be completely wrong on what it does.

but like you already figured out, make little changes at a time, and make sure you keep the old files in case something just doesnt go right with it. also good to track what you changed as well.

[MoeHorsePower]

Opening the blades drop the counts, closing the blades raise the counts..

[blkchevyz]

did you make any progress?