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

idle rpm

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Old Apr 12, 2006 | 05:42 AM
  #1  
limige's Avatar
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From: sebewaing, mi
idle rpm

when i reprogrammed my car i wanted to see what a lower idle would sound like. i set it at 875 rpm for both neutral and drive tables. (car is a 6 speed)

car idles at 950-1000 according to datamaster and shows 875 as the target rpm

why would it be idling so high? did i miss something??

mike

Last edited by limige; Apr 13, 2006 at 10:43 AM.
Old Apr 12, 2006 | 08:08 AM
  #2  
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Re: idle rpm

Is the coolant temp sensor input correct? That will affect idle speed. Is the VSS showing "0"? If it isn't, idle speed is elevated? Is the TPS showing "0%" and a closed throttle voltage less than 1.0V? Both those can elevate idle.

Is the IAC motor being commanded to close in response to the high idle? Is the IAC motor bottomed out at "0"?
Old Apr 12, 2006 | 10:55 AM
  #3  
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Re: idle rpm

i'll check those out, i know for sure that the tps was at 0% i'll double check the rest when i get home
Old Apr 13, 2006 | 09:33 AM
  #4  
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Re: idle rpm

ok
tps 0%
tps voltage .63
iac position 35

eng 78.5 deg C
oil 36.8 deg C

whats VSS?
Old Apr 13, 2006 | 09:47 AM
  #5  
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Re: idle rpm

Originally Posted by limige
ok
whats VSS?
Vehicle speed sensor
Old Apr 13, 2006 | 10:42 AM
  #6  
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Re: idle rpm

OK, VSS is zero..
Old Apr 13, 2006 | 04:00 PM
  #7  
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Re: idle rpm

Seems odd..... the PCM should be lowering the IAC counts in order to pull the idle down to 875rpm. If the IAC counts are at 35, and the idle speed is high, should keep reducing the counts.

Is it possible you are reading the "learned IAC counts" rather than the commanded IAC counts? Your scan data will include both.
Old Apr 13, 2006 | 08:52 PM
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Re: idle rpm

Originally Posted by Injuneer
Seems odd..... the PCM should be lowering the IAC counts in order to pull the idle down to 875rpm. If the IAC counts are at 35, and the idle speed is high, should keep reducing the counts.

Is it possible you are reading the "learned IAC counts" rather than the commanded IAC counts? Your scan data will include both.
Learned IAC counts? Which does Scanmaster LT-1 read?
Old Apr 14, 2006 | 05:11 AM
  #9  
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Re: idle rpm

i'm using datamaster, i only remember seeing one listing for iac counts. it started at 51 and dropped down to about 35..
Old Apr 14, 2006 | 01:43 PM
  #10  
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Re: idle rpm

Originally Posted by JPSartre12
Learned IAC counts? Which does Scanmaster LT-1 read?
Scanmaster reads the commanded IAC position.
Originally Posted by limige
i'm using datamaster, i only remember seeing one listing for iac counts. it started at 51 and dropped down to about 35..
If its moving, its the commanded position. Datamaster will record a column for "IAC target counts"..... I believe.
Old Apr 15, 2006 | 09:38 AM
  #11  
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From: sebewaing, mi
Re: idle rpm

now this may be related but i just installed new injectors (syty) tried 55#pressure and tuned for 34.6# injectors..
bank 1 Long terms when up to 160 and bank 2 went to 135 or so..
raised the fuel pressure to 75# and bank 2 came down to 128 but bank 1 is still 157 or something.

other than a possible intake leak what could cause this?
Old Apr 19, 2006 | 05:11 PM
  #12  
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From: Detroit Subs
Re: idle rpm

Originally Posted by Injuneer
Scanmaster reads the commanded IAC position.
Thanks. My Scanmaster shows my commanded IAC position creeps up to 160 on idle when warm.
Old Apr 20, 2006 | 11:09 AM
  #13  
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From: sebewaing, mi
Re: idle rpm

found a couple of cracked hoses off the tb. fixed that and things got better, gotta get a new power invertor and do some new datalogs.
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