[Supras] Increased idle with AC on?

[Rockey Fox]

Thank you Arlene, I remember well when you were very active on the list. In fact I have a folder titled "Arlene" where most of you posts are squirreled away as this one will be.
I have noticed the engine dies on me when I let off the throttle quickly but I'm fairly certain that is limited to when the AC is on so its likely related to the AC amplifier signal too.

Thanks again for the tip and as usual excellent description,

Rockey 91T


----- Original Message ----
From: "Lanman, Arlene" <arlene.lanman at okstate.edu>
To: supr91tt at yahoo.com
Cc: supras at supras.com
Sent: Wednesday, August 8, 2007 8:27:21 PM
Subject: Re: [Supras] Increased idle with AC on?




 
 

 

 

 


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Rocky,
 

  
 

I use to post quite often to Supras at supras.com, but my work
firewall denies me access, plus my work load is now phenomenal, not allowing me
much time to respond to questions.
 

  
 

  
 

The TCCS EDU controls the Idle Air Controller.
 

  
 

Inputs: Engine Speed (Ne), Throttle angle (IDL), Vehicle
Speed (SPD), Coolant Temp (THW), Neutral/Start switch position (NSW), Idle switch
(STA), Air Conditioner clutch (A/C through signal from the A/C Amplifier), Electrical
load (ELS), and Battery Voltage (=B).  
 

  
 

Controlled Parameters (via ISC control by the TCCS ECU)
include: Warm Curb Idle, Cold Fast Idle, Air Conditioner Idle-Up, Electrical
Load Idle-up, Automatic Transmission Idle-up.
 

  
 

Bottomline, miss with any of the inputs and the idle speed
changes due to change in the stepping motor position of the ISC.
 

  
 

Warm Curb Idle should be around 680 rpm, turning on the A/C should
increase the idle to around 900-1000 rpm.
 

  
 

If you turn on the A/C at warm idle and the A/C works but
the idle does not increase, check the signal out from the A/C Amplifier and
clean the ISC stepping motor mechanism.
 

  
 

In addition to the above, the engine speed input and
internal program of the ECU causes the ISC to “step down” in
increments when one releases the throttle in lieu of going from open throttle
to no air and engine kill when one lets off the gas.
 

  
 

Arlene Lanman
 

Stillwater,
 OK
 

-88T with a few mod
 

- Work Firewall does not allow me access to Supras at Supras.com
 



  
 




  
 

On Mon, Aug 06, 2007 at 06:20:35PM
-0700, Rockey Fox wrote:
 

  
 

> Pardon my ignorance but it
seems like the engine should increase idle 
 

> speed
 

above 600 rpm when the AC is on. I
was looking for the electric solenoid commonly used on American iron and didn't
see one on my Supra in the throttle linkage area. Is the ECU responsible for
increasing idle via ISC for this additional load?
 

> 
 

> Thanks,
 

> Rockey 91T M/T
 

  
 










       
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