High idle question
01-20-2008, 08:26 PM
#1
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High idle question Has anybody actually fixed their high idle issues with a clear objective solution? It seems that I've read quite a few posts of the same problem, but I haven't seen anybody actually solve it other than tuning it out...what is the usual culprit?
01-20-2008, 09:13 PM
#2
I still think its your IAC opening causing the high RPM, I think this because of 2 reasons;
1 You said in another post that you unpluged the IAC and ran around for a while like that with no high idle problems.
2 In your logs it shows the Iac open when the High idle happens.
I will try to get a screen shot up to show what I mean.
1 You said in another post that you unpluged the IAC and ran around for a while like that with no high idle problems.
2 In your logs it shows the Iac open when the High idle happens.
I will try to get a screen shot up to show what I mean.
01-20-2008, 09:21 PM
#3
Screen shot 
If I understand correctly, it looks like the sum of the total airflow through the Iac goes up when the Rpms are up... Dosen't this prove that the Iac is opening and causing the Rpms to go up?? Now you just need to find out what in the computer is causing the Iac to open.
01-20-2008, 11:22 PM
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I was loooking at this...
The MAP shows the loss of vacuum when I turned on the AC due to the IAC count nearly tripling allowing a signifigant amount of air to bypass the throttle blade.
Now here's my next question. In EFILive bidirectional controls the max value for IAC is 127. In this chart I show a value of 310. Anybody know the difference?
The MAP shows the loss of vacuum when I turned on the AC due to the IAC count nearly tripling allowing a signifigant amount of air to bypass the throttle blade.
Now here's my next question. In EFILive bidirectional controls the max value for IAC is 127. In this chart I show a value of 310. Anybody know the difference?
01-21-2008, 09:19 PM
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I don't know if they're the same metric or just values that are populated in the fields??
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01-21-2008, 11:09 PM
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More of the same...
If you create a chart with IAC steps, RPM, TP and IAC AC it sure is interesting. I don't know what it means, but it sure is interesting.
Everytime I turn on the AC the IAC counts go way up as does the idle. The IAC AC goes up a little. Once it goes into thigh idle the IAC step usually goes to 199 with an idle just above 2,000RPM, egage the clutch and the IAC step will got to 310 and idle over 3,000RPM. Turn off the AC and the idle will hunt around a little and then drop to normal with an IAC step count of 108ish. If I leave the AC off it drives normal.
If you create a chart with IAC steps, RPM, TP and IAC AC it sure is interesting. I don't know what it means, but it sure is interesting.
Everytime I turn on the AC the IAC counts go way up as does the idle. The IAC AC goes up a little. Once it goes into thigh idle the IAC step usually goes to 199 with an idle just above 2,000RPM, egage the clutch and the IAC step will got to 310 and idle over 3,000RPM. Turn off the AC and the idle will hunt around a little and then drop to normal with an IAC step count of 108ish. If I leave the AC off it drives normal.
01-22-2008, 02:03 AM
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I've been watching the TPS sometimes read .4% and sometimes Zero. I'm not sure if I may have a TPS issue, but it's certainly not what is causing this as I've seen the high idle event while the TPS was a solid 0.0%. I bought a new TPS today for cause, but I haven't opened yet as I'm not sure if I can adjust/reset ??? my old one? I have the new one ready to go if needed.
I need to see if the setscrew is holding it jsut enough to read .4% or the TPS is out of spec?
Since I don't have the tuning license all I can do is scan...
I need to see if the setscrew is holding it jsut enough to read .4% or the TPS is out of spec?
Since I don't have the tuning license all I can do is scan...
07-12-2008, 09:23 AM
#11
I'm new to LS1 Tech. My 99 Z28 is having a similar problem. I haven't traced the problem yet, but it is related to the A/C. The idle is crazy with the A/C on and normal with the A/C off. My car is stock - no mods at all. I thought it was a typical dirty throttlbe body/IAC port, so I cleaned them throughly, but that didn't help. I replaced the IAC motor and it acts crazier now than it did before.
07-12-2008, 03:41 PM
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There are numerous "limit" settings for how much air
can be added or taken out in the idle airflow (at least
in HPTuners, I presume similar in EFILive). If the airflow
base number is too high you may have limited ability
to trim down unless these are loosened up some.
The A/C adds airflow by its drag-torque calculations.
I see this stuff in the Engine>Torque Management
section. The A/C drag torque factors in head pressure
and IAT. The A/C torque model is probably realistic, but
the motor torque model on anything modded, is not.
I believe this is why A/C destabilizes modded vehicles'
idle worse than stock.
Look at your throttle follower for why IAC is swinging
wide under open throttle conditions. There's no real
use for follower that I can see. Maybe just a dash of
it, right off idle, but you don't need all it's doing.
can be added or taken out in the idle airflow (at least
in HPTuners, I presume similar in EFILive). If the airflow
base number is too high you may have limited ability
to trim down unless these are loosened up some.
The A/C adds airflow by its drag-torque calculations.
I see this stuff in the Engine>Torque Management
section. The A/C drag torque factors in head pressure
and IAT. The A/C torque model is probably realistic, but
the motor torque model on anything modded, is not.
I believe this is why A/C destabilizes modded vehicles'
idle worse than stock.
Look at your throttle follower for why IAC is swinging
wide under open throttle conditions. There's no real
use for follower that I can see. Maybe just a dash of
it, right off idle, but you don't need all it's doing.
07-13-2008, 08:41 PM
#14
See if you can find out how how much of your 4.23 lbs/min commanded airflow is base airflow, how much is AC offset, how much is long term and short term idle trims, and how much is from throttle follower. That would help a lot.
Also close your throttle using the set screw as much as possible and see if you can get that 0.4% throttle position to go back to zero. I know you said it does it when it reads 0.0% also, but it will cause problems based off of tps voltage, not just percentage.
Also close your throttle using the set screw as much as possible and see if you can get that 0.4% throttle position to go back to zero. I know you said it does it when it reads 0.0% also, but it will cause problems based off of tps voltage, not just percentage.