Idle screw

[Vettefan87]

I am trying to adjust the idle screw on my car but there is that cover that plumcrazy talked about in this thread http://www.corvetteactioncenter.com/forums/showthread.php?t=51102&highlight=TPS+voltage
He talks about adjusting the minimal idle, but there is a cover over the other end of the screw, my questions is, how do I remove it? Thanks


Justin

 

[rrubel]

Something like an awl or punch. Just poke through the plastic. You really don't need to have it in place (in fact, one article I read mentioned that if your idle speed had ever been adjusted before, the cap would be missing).
[RICHR]

 

[Ken]

You shouldn't have to adjust the screw; it's pre-set at the factory. The computer should control the idle speed, that's why the idle screw is sealed.

 

[vetteboy86]

We are trying to set the TPS sensor. We found a post by plumcrazy that says to adjust the idle to 400-450 in drive, and set the TPS that way. This is the reason why we need to get at the idle screw. It is pretty hard to get that cap out of there. Now that we know we can destroy the cap getting it out, it should be much easier.


Craig

 

[Ken]

The only way to get it out is to destroy it.

 

[vetteboy86]

Ken,

That is kind of what we figured. I usually dont mind working on other peoples cars, because destroying something is always an option. However my bro's vette, with him standing over me to destroy something is never an option.

Craig

 

[bradfordsvettes]

I believe the tps has some adjusment without removing the plug. there is a min air rate adjustment procedure in the manuel. before you pull the plug clean the throttle body and recheck your specs they may not be far off like ken said it is sealed for a reason and really should not need to be removed unless other changes have been made . only my 2 cents steve

 

[Vettefan87]

The car keeps stalling. Yesterday I started it up and it stalled three times before it actually started to run. Today I started and it it stalled once. I backed it out of the driveway let it sit for about a hour and a half to two hours, started it back up again, and it stalled. So I figured I would start here.

 

[tyrel]

I agree with Ken, even the service manual says to not fiddle with the idle screw. The ECM maintains idle, that's why the idle screw is sealed. If you are having idling problems, it is likely any number of things like IAC, TPS, vacuum leak, timing, so unless you address what is causing poor idle, you'll continue to have problems.

 

[Ken]

If you are having idling problems, it is likely any number of things like IAC, TPS, vacuum leak, timing, ...

Agreed! What have you checked so far Justin?

 

[Vettefan87]

Well I am not sure. I am getting no trouble codes so something can't be to far out of wack right? I adjusted the TPS to about .55 volts or so and the farthest I could get the idle to go to was like 700 RPM's, the throttle linkage would not return far enough to drop it any lower...? Other then that I am open to suggestions, The car did seem to run a tad better, but that might just be me.

 

[Ken]

Before we go any further, be sure to note that whenever servicing the IAC it should be disconnected and connected with the ignition in the "OFF" position. This will keep from having to reset the IAC.

The Idle Stop Screw used to regulate minimum idle speed of the engine, is adjusted at the factory, then is covered with a plug to discourage unnecessary adjustment.

Before checking minimum idle speed, be sure ignition timing is correct and, before making any idle adjustments, be sure throttle body is clean around the throttle plates.

Adjust

1. Pierce the idle stop screw plug with an awl and apply leverage to remove it.
2. Adjust idle stop screw assembly as required.
3. With IAC motor connected, ground diagnostic terminal.
4. Turn ignition "ON", do not start engine. Wait at least thirty seconds.
5. With ignition "ON", disconnect IAC electrical connector.

1. 
   
   !! IMPORTANT !!
   Disconnect the distributor set-timing connector.
   [*]Start engine and allow to go "Closed Loop".
   [*]Remove ground from diagnostic terminal.
   [*]Adjust idle stop screw to 450 rpm in neutral for manual or automatic transmision vehicles.
   [*]Turn ignition "OFF" and reconnect connector at IAC motor.
   [*]Adjust TPS, if necessary:
   
   • With ignition "ON", use a "Scan" tool and adjust TPS to obtain .54 volt +/- .08 volt.
   • Tighten screws, then recheck reading to insure adjustment has not changed.
   [*]Start engine and inspect for proper idle operation.

 

[KANE]

We are trying to set the TPS sensor. We found a post by plumcrazy that says to adjust the idle to 400-450 in drive, and set the TPS that way. This is the reason why we need to get at the idle screw. It is pretty hard to get that cap out of there. Now that we know we can destroy the cap getting it out, it should be much easier. Craig

I adjusted my TPI's idle on my old vette to give it a "tactical" idle. You need to adjust the IAC and the set screw so the computer won't fight with the speed you have set it at.

I wanted 750 rpm in drive. This way, the idle would be high enough to load the tranny easier. It helps your take off from a light just a little bit better, not by much- but I think it helps a little. People may say you waste gas with a high idle... but who cares. You only live once.

 

[vetteboy86]

I think we should see an improvement over cold starts. When i checked the TPS sensor voltage in it's old position it was nearly .44 volts. So according to the posts here and the manual that is over 100 millivolts difference. Hopefully there will be a difference in the way it starts cold.


Craig

 

[First C4]

While adjusting the idle screw and TPS properly will solve some problems you MUST first remove your throttle body and properly clean behind the throttle plates. You should also clean your IAC valve. After all this is completed only then should you perform the idle screw and TPS adjustments. In some cases the only reason for high idle is the grime that is built up behind the throttle body. I do not believe in the K&N air filters because over time improper cleaning and oiling of the filter causes the oil to be deposited into the throttle body increasing the speed at which the throttle body gets gunked up. A proper cleaning and adjustment should solve most problems.

 

[vetteboy86]

His motor was rebuilt only a few months ago. We cleaned the throttle body, and he did some porting of the plenum. We did find that the throttle screw was tampered with. It did have markings on it to show that it had been adjusted. However the cap was new, so somebody replaced the cap. I only performed the TPS adjustment when I found it to be off. The correct voltage is 540 millivolts. His was set at about 440 millivolts. We adjusted it to the correct value.


Craig