Simple Question
Thread Starter
Intermediate
Joined: Jun 2011
Posts: 34
Likes: 0
Simple Question
corvette 1993, i adjusted the idle srew to lower the engines RPM levels. after i started the car, i checked and it was too low. now im trying to turn the screw the other way but its stuck. is there another way i can turn the screw? i turned the screw using a needle nose pliers, now its stuck. what should i do?
Last edited by Jason.RG16; Dec 29, 2011 at 06:55 AM.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Adjust screw is turned from the rear with a small Torx head bit.
If never been adjusted before ,you need to remove the cap that seals the screw head 1st
Did you disconnect the IAC when adjusting idle?
Last edited by rodj; Dec 29, 2011 at 07:45 AM.
Thread Starter
Intermediate
Joined: Jun 2011
Posts: 34
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yeah i did disconnect the IAC. i had the Torx head, but i couldn't find a way to get it in the back, il try with the torx, maybe it will still turn. i hope i dnt mangle the threads too much. Can u specify what number torx? thanks
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
FYI, Those are set at the factory and should not need to be messed with. If you got an idle problem, fix the real issue.
I had a high idle on a buddies 94, because some idiot decided to mess with the stop, caused all kinds of grief.
I think it is a T20, and it is a tamperproof torx not a regular one. Has a raised bump in the middle of the torx pattern.
I had a high idle on a buddies 94, because some idiot decided to mess with the stop, caused all kinds of grief.
I think it is a T20, and it is a tamperproof torx not a regular one. Has a raised bump in the middle of the torx pattern.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
I disagree that the minimum throttle opening shouldn't ever need adjustment. I always felt the same way until my car started dying at idle. I did the minimum idle adjustment and have never had a problem since then. Mine is a regular Torx T-20, not a security type.
I think the linkage becomes worn over time and allows the throttle plates to close more than they should. On my car there is definitely some metal deformation where the adjusting screw contacts the linkage.
I think the linkage becomes worn over time and allows the throttle plates to close more than they should. On my car there is definitely some metal deformation where the adjusting screw contacts the linkage.
Drifting
Joined: Jun 2010
Posts: 1,853
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From: Westerly RI
One issue that can lead to high idle after many miles is wear on the throttle plate shaft. This allows extra air into the plenum, then the ECM adds fuel to reach stochiometric air/fuel mixture, resulting in high idle speed. You can diagnose this by reading the "counts" value for the IAC with a scanner, if the valve is closed, and the idle is too high, look for an air leak around the throttle body, or a vacuum leak elsewhere. You can also do a crude representation of this test by removing the air inlet and carefully taping over the bores, but not the little hole between them, to see if there is any major change to the idle speed.
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
One issue that can lead to high idle after many miles is wear on the throttle plate shaft. This allows extra air into the plenum, then the ECM adds fuel to reach stochiometric air/fuel mixture, resulting in high idle speed. You can diagnose this by reading the "counts" value for the IAC with a scanner, if the valve is closed, and the idle is too high, look for an air leak around the throttle body, or a vacuum leak elsewhere. You can also do a crude representation of this test by removing the air inlet and carefully taping over the bores, but not the little hole between them, to see if there is any major change to the idle speed.
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Race Director
Joined: Apr 2000
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From: Texas
Just to be clear, the OP was attempting to adjust the idle speed via the screw on the throttle body. The idle speed is programmed into the ECM. The screw adjusts minimum idle air so that the IAC is within range.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
http://forums.corvetteforum.com/1548110758-post6.html
Most often mentioned method for idle adjustment
https://www.corvetteforum.com/techti...D=55&TopicID=2
Revised vesion
http://www.corvetteactioncenter.com/...-corvette.html
Last edited by rodj; Jan 1, 2012 at 02:55 AM.