TB Idle Screw...

johnathan1

johnathan1

Supra =
Aug 19, 2005
5,056
1
36
36
Downey, California, United States
How exactly does this little screw work? As I'm sure some of you have read a while back, I had a HUGE "Idling at 1k" thread... and my idle problem hasn't changed a bit until today...I got frustrated, and said screw it and adjusted the screw...

I turned it to the right about 1 1/2 turns until the idle was around 650-700, and it seems fine. The idle goes to about 900-1k with the A/C on, returns to ~700 when turned off...is there anything wrong with this?

So...what is the ideal setup w/ the screw? Should it be all the way in or out or what? Or is it okay to use it to adjust idle?
 
wingman

wingman

sucka got blammed!
Sep 11, 2005
427
0
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35
Phoenix, AZ
it controls the resting angle of the throttle plate when you let off the throttle....your ISC should compensate for any adjustment made using the screw though. I just leave mine alone.
 
Joel W.

Joel W.

Just A Jedi
Nov 7, 2005
1,561
0
0
Washington
johnathan1 said:
the idle was around 650-700, and it seems fine. The idle goes to about 900-1k with the A/C on, returns to ~700 when turned off...is there anything wrong with this?
Click to expand...

That sounds correct to me.. What was it before your screw adjustment with the AC off?
 
G

gixxer750

2jzget comingsoon!
Mar 30, 2005
2,333
0
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Mississippi
The screw on the side of the throttle body does NOT control the angle of the throttle plate...at least not on a pre 89.

The screw opens and closes an orfice designed to bypass air around the throttle plate. From what I can tell, the screw is used to set a baseline for the ISC to work around.... I.E... you can adjust the idle with it.


Personally, I like my car to idle at 900RPM....because it has 25 psi of oil pressure there.
 
johnathan1

johnathan1

Supra =
Aug 19, 2005
5,056
1
36
36
Downey, California, United States
Thanks, JetJock...I guess I had forgotten, lol. That's good that it is working normally now.

I tried to screw it all the way in, but the car would go down to about 400RPMs, and would act like it was going to die...
 
Racefiend

Racefiend

OH, YEAAHH!
Apr 6, 2005
106
0
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47
Bay Area, CA
I agree with both Gixxer and jetjock. However, I will add a few pennies to the pot.

After rebuilds or head work, I have always found the need to adjust idle using the screw. First of all, adjust all throttle body/tps settings to spec. Then let it run for a while to let the ecu learn engine parameters (I usually wait a day or so, unless the idle is so bad it needs initial adjustment right away. But that's usually not the case if you're reusing your old TB). Next I put the ecu in diag mode, and adjust idle and timing to specs. Remember, idle changes will affect timing, and vice versa.

I've never had a problem with this method and idle stays rock solid.
 
TurboWarrior

TurboWarrior

New Member
Apr 1, 2005
763
0
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42
Canada
Idle:

650rpm Turbo
700rpm NA

Idle on mine always jumped to 1100 with the ac on. about 800-900 with the headlights on. at first anyway.

I was going to post about having a high idle. It was at 1100 all the time and i spent a few hours going through the manual. But then i drove it for a day and it hasn't done it since. I guess thats all it needed.
 
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