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Thread: After start up idle drop

  1. #1
    Senior Member Naf's Avatar
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    Default After start up idle drop

    I have upgraded my MAF from the stock tube to a 102mm, using the same sensor. I have calibrated the sensor to be perfect and the truck starts up with no a/c perfectly. If and when i start up with the A/C on the truck will start up, rev to about 1250rpm, steadily drop to 1000rpm then rapidly drop to just about 400rpm, it will then recover by over revvin to 1500rpm and settlin at the desired idle speed.

    I checked the WB and it showes 8 afr at startup, then 14.6 afr after startup then 9 afr during the sudden rpm drop. and back up to 14.6 afr durin the constant idle time.

    Its my work truck and loggin the data with a WB take a while, and i apologize for this.

    Does anyone know why this is happenin?
    American Muscle, European Design, Japanese Tactics

  2. #2
    Senior Member Naf's Avatar
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    Quote Originally Posted by Naf View Post
    I have upgraded my MAF from the stock tube to a 102mm, using the same sensor. I have calibrated the sensor to be perfect and the truck starts up with no a/c perfectly. If and when i start up with the A/C on the truck will start up, rev to about 1250rpm, steadily drop to 1000rpm then rapidly drop to just about 400rpm, it will then recover by over revvin to 1500rpm and settlin at the desired idle speed.

    I checked the WB and it showes 8 afr at startup, then 14.6 afr after startup then 9 afr during the sudden rpm drop. and back up to 14.6 afr durin the constant idle time.

    Its my work truck and loggin the data with a WB take a while, and i apologize for this.

    Does anyone know why this is happenin?
    Here is a log minus the Wb...
    American Muscle, European Design, Japanese Tactics

  3. #3
    Senior Member Naf's Avatar
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    Found out what my problem was...

    I tuned the MAF with an open loop ben factor to be around the currect afr value. so i was gettin the amount of air the MAF was registerin.

    If you have a uncalibrated MAF follow the idle instructions, However, if you took the time and calibrated properly, then you may return all your idle settings to stock, or close to stock...

    I am runnin a 226/236 cam and 550lift at the valves. Idle settins are stock and it loops just the same as it did with the restricted idle settings. But i can start the truck remotely with the AC on and it will not dye after initial start, and it also doesnt surge when i am stuck in traffic
    American Muscle, European Design, Japanese Tactics

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