'Idle speed control actuator'

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udidwht

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The 'Idle speed control actuator' in my pic is a vacuum can (see my pic left of TBI). It is controlled by the 'EGR valve control solenoid' (under Exhaust/Emissions' category Rockauto). This is just to the left of the PCV in my pic.

Part# Standard Motor products VS6

or

Wells Vehicle electronics 2F1121

Idle Speed/Throttle Actuator - Vac-Mechanical (aka throttle kicker)

Description and Operation:

Purpose: The idle speed control actuator system assists the idle air control system in controlling the idle speed, primarily at cold temperatures.

Operation: The idle speed control actuator is a vacuum operated device which opens the throttle slightly (2 to 3 degrees of angle) to increase the cold engine idle speed, to improve the mixing of the air and fuel, and to allow lower warmed up engine idle speeds. The idle speed control actuator is controlled by the EGR valve control solenoid, which is controlled by the power control module. To increase the idle speed, the EGR valve control solenoid is turned "OFF," and no vacuum is routed to the idle speed control actuator, allowing it to open the throttle slightly. To decrease the idle speed, the EGR valve control solenoid is turned "ON" and vacuum is routed through the solenoid to the idle speed control actuator, allowing the throttle to fully close (warm engine).

In conjunction with the idle speed control actuator system, the idle air control continuously monitors and controls the engine idle speed to the desired idle speed. A Tech 1 scan tool will read the control module commands to the idle speed control actuator system.

The throttle actuator provides another function. The larger the TB, the more the bores expand as the engine gets hot. The 92+ 454 equipped truck ran much hotter than the older square body version. And GM had switched to a heated intake instead of the small heater plate, which was much more effective at heating the TB and keeping it warm after the engine was shut off. Well, a larger bore means the throttle plate must be closed more to keep idle speed low. No problem, right? Just reduce minimum air by turning the throttle stop and you're done. But if you do that when the engine's hot, the next day when you go to press on the accelerator while the engine's cold, the throttle plate is stuck. Not so good. The throttle actuator allowed a way to reduce idle speed when hot yet keep the throttle far enough open when the engine was off so a cooling TB wouldn't seize the plate.

This was not installed on all TBI set ups but was on the truck variants. Unsure exactly of what years but I believe 90-95 454s.


Pic of my 1994 TBI 454:
https://www.dropbox.com/s/ow3nt7k4hf4gimd/201 80512...

Anyone hear have off hand the adjustment procedure/s for these item/s?

And lastly anyone know if the vacuum can is available anywhere?
 

GoToGuy

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You have the description and operation, the next logical paragraph would be adjustment. Where is it? Service manual emissions section?
 

udidwht

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Ran across the following here: https://www.gmt400.com/threads/help-me-id-these-parts-please.41025/

Idle Speed Control Actuator Adjustment
Procedure:
  • Before adjusting ISC actuator you must first check the minimum idle speed to be within specifications. Refer to SPECIFICATIONS/IDLE SPEED. (ISC actuator must have vacuum applied so that it is not contacting the throttle lever.) See image VIEW A.
  • Remove vacuum hose on ISC actuator on warm engine.
  • Adjust ISC actuated idle speed to 1300 +/- 50 rpm. See image VIEW B.
  • Install vacuum hose.

This what you see in the manual?
 

Caman96

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Find your manual here:
 

udidwht

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Find your manual here:
Which would suffice for a 1994 GM P-30 chassis (454 TBI w/4L80E)?
 

udidwht

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In the event this vacuum can is leaking and one can't be source what would be the work around?

I've heard getting to the 'Idle adjustment screw' that is covered and turning it open roughly 1 turn would be the work around. Anyone know if this is true?

Odd that the vacuum can isn't available anywhere.
 
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