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When I make changes to the idle parameters does the PCM need a learn time?

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Old 03-12-2005, 06:40 PM
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Red face When I make changes to the idle parameters does the PCM need a learn time?

I have a question after cam install. Already went thru the setting of the TB screw. When I make changes to the idle parameters does the PCM need a learn time? How long should I wait before each change? I did 21 flashes today and ended up going back to the third one. If the PCM needs to relearn I will have to start all over. Right now it idles OK after it finds idle. It still surges up and down. I guess I just need to keep trying to get it right. I just wanted to make sure the PCM does not need learn time.

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Bill

Old 03-12-2005, 06:53 PM
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Your LTITs need to re-learn. You need to log LTITs and STITs before making any base running airflow changes. LTITs can screw you up really badly.
Old 03-12-2005, 06:59 PM
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Before the cam the LT's were all negative. I am just trying to get the thing to idle in gear without surging or going into cruise control.
Since I have changed my VE table and timing table I guess I need to do some relearning to see where the LT and ST are now.

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Bill
Old 03-14-2005, 09:08 AM
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LTIT = Long Term Idle Trim

LTFT = Long Term Fuel Trim

two entirely different beasts!!

when you change anything related to idle RPM or idle airflow, you must let your LTITs settle out to a steady state value (also check they are not hitting the calibration limits). LTIT and STIT are something we added to the scanner with v1.6.0. You can find them (and a bunch of other idle PIDs) under "Engine -> Idle" in the insert PID list.

Chris...
Old 03-14-2005, 10:04 AM
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You can zero out the LTITs by pulling the PCM fuses. On a Vette there are 2 under the hood.Pull them for 4-5 minutes. @ minutes is not long enough with my car. FWIW.
joel
Old 03-14-2005, 10:09 AM
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@ = 2 I do believe..
Old 03-14-2005, 11:11 AM
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Originally Posted by Another_User
Your LTITs need to re-learn. You need to log LTITs and STITs before making any base running airflow changes. LTITs can screw you up really badly.
I did not know there were LTIT's. I know now. How long does the relearn take?

Bill
Old 03-14-2005, 12:40 PM
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Originally Posted by Black02SS
@ = 2 I do believe..
uhh, yes, sorry. I stink at typing...two finger typer!!

I read slow too............... guess it works out!
Old 03-14-2005, 12:41 PM
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Originally Posted by Bill Bowling
I did not know there were LTIT's. I know now. How long does the relearn take?

Bill
Takes about 45 minutes on my car.
Old 03-14-2005, 04:05 PM
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Originally Posted by gameover
LTIT = Long Term Idle Trim

LTFT = Long Term Fuel Trim

two entirely different beasts!!

when you change anything related to idle RPM or idle airflow, you must let your LTITs settle out to a steady state value (also check they are not hitting the calibration limits). LTIT and STIT are something we added to the scanner with v1.6.0. You can find them (and a bunch of other idle PIDs) under "Engine -> Idle" in the insert PID list.

Chris...
While we are chatting idle, is it my imagination, or does MAF airflow directly affect your running airflow calculations?




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