IAC are slow to go down after stopping
06-14-2011, 02:31 PM
#1
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IAC are slow to go down after stopping Help me fix an issue.
When I am driving along my IAC are 117, when I come to a stop they are very slow to come down to zero (about 4 to 5 sec), my normal idle spot.
I have reduce the Throttle Cracker Airflow table to 0 in all cells from 400 to 2800rpm and 0 to 16 MPH.
Is there any other adjustment that can cause the IAC to hang up so long?
When I am driving along my IAC are 117, when I come to a stop they are very slow to come down to zero (about 4 to 5 sec), my normal idle spot.
I have reduce the Throttle Cracker Airflow table to 0 in all cells from 400 to 2800rpm and 0 to 16 MPH.
Is there any other adjustment that can cause the IAC to hang up so long?
06-14-2011, 02:43 PM
#2
Help me fix an issue.
When I am driving along my IAC are 117, when I come to a stop they are very slow to come down to zero (about 4 to 5 sec), my normal idle spot.
I have reduce the Throttle Cracker Airflow table to 0 in all cells from 400 to 2800rpm and 0 to 16 MPH.
Is there any other adjustment that can cause the IAC to hang up so long?
When I am driving along my IAC are 117, when I come to a stop they are very slow to come down to zero (about 4 to 5 sec), my normal idle spot.
I have reduce the Throttle Cracker Airflow table to 0 in all cells from 400 to 2800rpm and 0 to 16 MPH.
Is there any other adjustment that can cause the IAC to hang up so long?
06-14-2011, 03:38 PM
#3
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They shouldn't be going to zero. Part of your problem is you don't have the BRAF correct, and when you stop, the computer has to use the idle trims to pull it down. So, upon decel, your airflow adder tables have to decay, then when stopped, the trims have to pull it down.
I can close the throttle blade to bring the counts up to 40 to 60, will that help?
The engine always seams to idle a few hundred below low my target idle rpm, but it is solid at idle.
Motor is a 442ci NA motor with 14.3cr, Cam is 274/295 with .800 lift on e85. motor runs and drives good with only 3 issues. 1st is the it is always idling a few hundred rpm below target, 2nd it idle hangs when car comes to a stop and finally small bucking below 3,000rpm which i was able to greatly reduce by pulling out some timing.
Thanks for the help.
06-14-2011, 04:35 PM
#4
Ok, so how do I go about correcting that.
I can close the throttle blade to bring the counts up to 40 to 60, will that help?
The engine always seams to idle a few hundred below low my target idle rpm, but it is solid at idle.
Motor is a 442ci NA motor with 14.3cr, Cam is 274/295 with .800 lift on e85. motor runs and drives good with only 3 issues. 1st is the it is always idling a few hundred rpm below target, 2nd it idle hangs when car comes to a stop and finally small bucking below 3,000rpm which i was able to greatly reduce by pulling out some timing.
Thanks for the help.
I can close the throttle blade to bring the counts up to 40 to 60, will that help?
The engine always seams to idle a few hundred below low my target idle rpm, but it is solid at idle.
Motor is a 442ci NA motor with 14.3cr, Cam is 274/295 with .800 lift on e85. motor runs and drives good with only 3 issues. 1st is the it is always idling a few hundred rpm below target, 2nd it idle hangs when car comes to a stop and finally small bucking below 3,000rpm which i was able to greatly reduce by pulling out some timing.
Thanks for the help.
06-14-2011, 04:56 PM
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Once warm it idles with it closed to 5.
Cold start are great as with all other idle except when rolling to a stop it stay up 500 to 600 rpm for 4 to 5 seconds with the IAC showing 117 steady then rolling down towards zero.
06-14-2011, 05:35 PM
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I am use HPT and their scanner.
If I raise the idle with the TB set screw it will raise up fine, but if I reduce the idle screw to have the IAC pick up the idle it will be a few hundred low but idles good but I rather have it idling higher.
Not sure if it the high RPM I am shooting for is the issue or not. I am shooting for a idle around 1,450rpm but it hang around 1,250.
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06-15-2011, 01:00 AM
#8
You may have to adjust alot of idle tables to get the IAC to work correctly depending on your TB.
06-15-2011, 07:38 AM
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I have it commanded at 1,450 but idles around 1,250 to 1,300.
It's a 900hp na motor with a very large cam, sheet metal intake and 115mm TB. It can idle lower no problem but it is smother and easier on the valve train a little higher.
The tune is a SD, what idle table are you referring to?
06-15-2011, 09:20 AM
#12
It idles good, just 200 lower then commanded and the idle hang high when I roll to a stop.
I have it commanded at 1,450 but idles around 1,250 to 1,300.
It's a 900hp na motor with a very large cam, sheet metal intake and 115mm TB. It can idle lower no problem but it is smother and easier on the valve train a little higher.
The tune is a SD, what idle table are you referring to?
I have it commanded at 1,450 but idles around 1,250 to 1,300.
It's a 900hp na motor with a very large cam, sheet metal intake and 115mm TB. It can idle lower no problem but it is smother and easier on the valve train a little higher.
The tune is a SD, what idle table are you referring to?
Using your histograms, plot the Idle Airflow-Desired airflow.
Still need to set it up to be around 40 IAC counts when warm. Without seeing the tune, it's hard to say what other parameters need changed. Things like ETC scalar, and parked IAC flow impact IAC performance, and susequently, off idle performance, and return to idle performance.
