Air flow meter air by-pass passage screw - FJ62/3fe (1 Viewer)

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Does anyone know the function of this screw? It is similar in appearance to the Golden Screw on the throttle body, but the FSM does not mention its function, just identifies the chamber that it is sunk into as the "air by-pass passage." I also find only one thread on Mud that mentions it. When I bought my truck the screw was not seated all the way down nor screwed all the way out. I have read that the throttle body Golden Screw is not designed for user adjustment, just for factory calibration. Thoughts?

Context: I am chasing down a rough idle (which has become a high idle after the installation of a new fuel pressure regulator). The steps I have taken during the process are too numerous for this post.
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Spook50

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Going to follow this thread. I've never messed with mine, but had always assumed it had something to do with calibration of the AFM.

I've read in the past that folks who have put bored out throttle bodies on have removed the AFM cover and actually adjusted the mechanism inside to compensate for the increased airflow. Had wondered if this screw would accomplish the same thing or no.
 

Dynosoar

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Your intake tube looks worse for the wear. the silicone on the nipple looks sus.
 

EscapeWagon62

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Well well....Ive torn my engine compartment apart several times and not once did I notice the screw you just pointed out! Learn something new everyday. That being said I doubt that is where you want to look for a fix.

Regarding the ability to adjust the brass screw in the TB....everyone does it. I do recommend installing a new O ring on it as the one thst is there is likely old and cracked and can let air in.

My theory having chaced and eventually solved my rough snd high idle issues (over time, not my first try)
1. Your old fuel pressure regulator inhibited flow, you replaced it and are now idling higher.
2. The PO adjusted several systems to account for that bad pressure regulator and several items are out of whack.

I would start with
1. Re-set timing to 7 degrees.
2. Run the test sequence for your throttle position sensor. Reset as needed
3. If it is rough idle when warmed up....check/replace the temperature sensor on your thermostat water housing. Thst happened to me where the engine was hot but the computer thought it was cold.
4. It timing and TPS are set correctly and idle is still high you have an air leak.

Good luck
 
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High idle solved. Pro tip: if you move your throttle cable while working on something else in the engine bay, make sure you move it back when you’re done or you may end up riding around wondering why your RPMs are at 2,000. :doh:
 

Spook50

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High idle solved. Pro tip: if you move your throttle cable while working on something else in the engine bay, make sure you move it back when you’re done or you may end up riding around wondering why your RPMs are at 2,000. :doh:
I did EXACTLY that a couple weeks ago when adjusting my dash pot. Bonked the throttle cable bracket and didn't realize it until I investigated the high idle after a drive around the neighborhood.
 

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