Computer Diagnostics and Tuning Technical discussion on diagnostics and programming of the F-body computers

Drops in RPM when coming to a stop???

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Old Mar 3, 2006 | 11:05 AM
  #1  
gamecockfan04's Avatar
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From: South Carolina
Drops in RPM when coming to a stop???

After my Hotcam and Stall, Im having a issue when I come to a stop the car drops in RPM, to almost stalling, then corrects itself. Ive been told to change the table w/tunercat under Main Spark Advance, but need to know whether to increase the numbers, or reduce them. Is this right or is there something else to it?
Old Mar 3, 2006 | 12:40 PM
  #2  
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Re: Drops in RPM when coming to a stop???

Yeah thats not right. You might be able to help it by changing the IAC steps(increase them) I believe. Basically whats happening is the IAC isnt opening up fast enough to keep up with the air demanded by the motor to retain the idle. If increasing the steps doesnt work then you can pull off the throttle body and drill a slightly larger IAC bypass hole to let more air bleedy past the IAC so it doesnt have to work so hard. The IAC bypass is already there on the stock TB in the middle just below center... go a hair larger till the problem clears up and too big isnt good either.

I also see you have an air foil. Get rid of that thing. It blocks air flow to the IAC and to the PCV system... just removing that worthless mod could fix the problem.
Old Mar 3, 2006 | 01:08 PM
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gamecockfan04's Avatar
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Re: Drops in RPM when coming to a stop???

Sorry need to change my sig. I got rid of that piece of Crap Air Foil long ago. I was just told that reducing, or either raising the timing was the problem.
Old Mar 3, 2006 | 04:44 PM
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Re: Drops in RPM when coming to a stop???

Originally Posted by gamecockfan04
Sorry need to change my sig. I got rid of that piece of Crap Air Foil long ago. I was just told that reducing, or either raising the timing was the problem.
Right and Im telling you that is wrong. Its a matter of starving the motor of air(most likely) because of an IAC that isnt working correctly.
Old Mar 4, 2006 | 12:44 PM
  #5  
mike 96 ws6's Avatar
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Re: Drops in RPM when coming to a stop???

Just for kicks, you may want to pull the IAC motor an clean her up just to be sure. Usually a pintle not seating will cause the opposite, {too much air} but it wouldn't hurt to check it before you drill the TB but then you probably are already ahead of me on that. .
Old Mar 6, 2006 | 01:00 PM
  #6  
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Re: Drops in RPM when coming to a stop???

...which TB do you have? Mine was doing the same thing. Opening up the throttle blades a little bit with the adjustment screw cured mine.
Old Mar 7, 2006 | 10:00 AM
  #7  
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Re: Drops in RPM when coming to a stop???

Opening up the throttle blades a little bit with the adjustment screw cured mine.
DITTO
Old Mar 8, 2006 | 09:21 AM
  #8  
gamecockfan04's Avatar
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Re: Drops in RPM when coming to a stop???

Its the stock 48mm TB, but I did kinda mess around with the TB set screw and may have closed it too far.
Old Mar 8, 2006 | 10:25 PM
  #9  
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Re: Drops in RPM when coming to a stop???

definitely play around with the set screw before you start drilling lol
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