throttle set screw
#1
01-07-2015 | 05:11 PM
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throttle set screw
I have a 93 f150 5.0 and I'm having trouble with my throttle set screw. I had someone try helping me timing my truck and they decided to unscrew the set screw to adjust the throttle. Does anyone have an idea upon how to correctly set the throttle set screw?
#2
01-08-2015 | 10:46 AM
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Joined: Jul 2006
Posts: 7,489
Welcome to the site..
Technically it's not an idle screw. Idle speed is controlled in part by the PCM, EFI, and intake air metering done with IAC (idle air control solenoid/motor) Fuel (pulse width of the injectors) and air (IAC) are PCM controlled. The Intake plate "generally" is just held open far enough with the stop screw to keep the plate from wedging/binding in the throttle bodies bore. If the
idle speed was out of specs, it probably wasn't related to the plate. Although, sometimes a worn out throttle body can stick the throttle, or, excessive carbon/goo buildup in the bore and on the plate, or within the IAC itself can affect idle speeds. Could be a few reasons for a low/high idle speed. CEL on?
Technically it's not an idle screw. Idle speed is controlled in part by the PCM, EFI, and intake air metering done with IAC (idle air control solenoid/motor) Fuel (pulse width of the injectors) and air (IAC) are PCM controlled. The Intake plate "generally" is just held open far enough with the stop screw to keep the plate from wedging/binding in the throttle bodies bore. If the
idle speed was out of specs, it probably wasn't related to the plate. Although, sometimes a worn out throttle body can stick the throttle, or, excessive carbon/goo buildup in the bore and on the plate, or within the IAC itself can affect idle speeds. Could be a few reasons for a low/high idle speed. CEL on?
Last edited by Hayapower; 01-08-2015 at 10:49 AM.
#3
01-08-2015 | 12:51 PM
Junior Member
Joined: May 2010
Posts: 9
Idle problem with 5.0
Had a fast-idle problem for about 3yrs -kept getting faster over a long period I replaced several parts easy to get to with no results. I felt like it was a air leak behind throttle plates. Finally found someone to replace the Plenum gasket and it took care of the fast idle - it was up to 2000rpm! now normal
#5
01-09-2015 | 12:03 AM
Super Moderator
Joined: Jul 2006
Posts: 7,489
The 'in part' of my message didn't eliminate TPS.
CEL question, leaning towards intake/un metered air, lean or rich conditions affecting speed, or TPS range issues.
You mentioned they 'backed out' the stop which can stick the plate/s in their bore. If it were backed out, usually a simple adjustment back just enough to tip the plate/s is all that's needed for a correction. The stop is adjusted to just let 'minimal' air flow pass. Curb idle and fast idle speeds are controlled by PCM and the Idle Air Control valve.
A large increase or decrease in closed plate airflow from the calibrated level, won't let the devices effectively control the speed.
The TPS numbers should be approx. 0.601-4.538 no drop outs in between..
CEL question, leaning towards intake/un metered air, lean or rich conditions affecting speed, or TPS range issues.
You mentioned they 'backed out' the stop which can stick the plate/s in their bore. If it were backed out, usually a simple adjustment back just enough to tip the plate/s is all that's needed for a correction. The stop is adjusted to just let 'minimal' air flow pass. Curb idle and fast idle speeds are controlled by PCM and the Idle Air Control valve.
A large increase or decrease in closed plate airflow from the calibrated level, won't let the devices effectively control the speed.
The TPS numbers should be approx. 0.601-4.538 no drop outs in between..
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