woody3882

I just installed a new TPS & IAC on my 1994 LT-1 and found that I needed to adjust the Idle a bit. I took out the set screw plug from the throttle body but I can not figure out what size/tool fits into the opening to turn the idle set screw. I used a mirror and flashlight and believe I see a small torx, but there is no way to fit a torx screw driver in because of the shape of the outer body.
Is there a special tool or screw driver to fit into the opening to adjust the idle speed screw on my 1994 LT-1 If so what size is it
Thanks I appreciate any help
Woody

A Peter C4

Someone needs to help this guy before he damages his car. Get a FSM and study it.

woody3882

I do have Both manuals, and no where in the books does it state, after the plug is removed, (which it was when I purchased the car 5 years ago) what size torx, (or what ever tool) will fit in the throttle body housing to adjust the RPM Idle Set Screw. I am very familiar with the installation and calibration of the TAC and the IAC. I am trying to adjust the errors of previous owners.
So before this gets out of control, Simple Question Please: what size torx, (or what ever tool) will fit in the throttle body to adjust the Idle Set Screw after the plug has been removed.

FrankieD

If i recall correctly it's a Torx T-20

MatthewMiller

I think what they are getting is that your idle speed isn't really set by the set screw, but rather by the computer acting through the IAC. Typically, the set screw should be set so that the engine just barely dies with the IAC unplugged. But the IAC is what's going to modulate how much air is entering the plenum, once you plug it back in.

woody3882

That is what I was looking for
Thanks Matthew & FrankieD much appreciated

aklim

Why would you need to adjust your idle? That is a process that goes through the computer and needs to be programmed.

A Peter C4

That's what I was trying to say, computer sets the idle.

aklim

And if you try, you can jack it up to the point the ECM cannot work but......

woody3882

The set screw has been previously backed off so there is a slight gap between the tip of the screw and the throttle lever. In order to properly set the TPS the set screw should be barely touching the lever plus 1/4 of a turn. I am just trying to correct the bad ways of the previous owner. After the set screw is properly adjusted, I can calibrate the TPS to the recommended .67 volts

WVZR-1

Minimum idle air I thought used this or very similar procedure. If link doesn't open to #5 scroll to it. Searching "minimum idle air" should work. FSM just mentions "factory set". I believe I've seen it mentioned before to jumper the ALDL to put ECM/PCM in diagnostic mode. Maybe that's only required on earlier TPI.

https://www.corvetteforum.com/forums...post1550202163

The T-20 was correct wasn't it?

aklim

I don't think that is the way to set up the minimum idle. TPS voltage is 0.54

aklim

At the factory, everything is in spec so that way works. 20 years later, well...... I would set it up with a scanner for about 20 to 30 IAC counts.

Before I do this, I would clean up the throttle body since I suspect something is sticking

woody3882

Not sure on the Torx t-20 as of yet, as you know, because of the configuration I have to get a t-20 and heat/bend the shaft to a 90 degree angle to fit it in the hole. Also I currently do have a new TPS & IAC, the throttle body has been cleaned. The only confusing part is what voltage to set the TPS to. in all of the threads I read I have heard, .45, .50, .54, .65, .65 as of last night I set it at .65 and the set screw is 1/4 turn on the lever. I have an idle in park at about 750 and in drive at 550 That is a lot better than the 1200-1500 idle in park that is was. I did learn that the TPS and the IAC do work in conjunction with each other, so I would recommend that if you do replace one, definitely replace the other.
I am grateful and appreciate all the input from the forum members.
Thanks

aklim

To set up that way, the thing is the tach has to be right, no timing issue and no air leaks and the motel has to be working as planned and not necessarily as it feels good. Timing first, air leaks and scanner to see rpm and then TPS. You do NOT have to replace both IAC and TPS

A Peter C4

Sounds like you did a good job correcting the idle issue.