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limey222
Michael Cubbon
Portland, OR
(129 posts)

Registered:
08/01/2015 12:55PM

Main British Car:
1969 MGB GM 3.4L V6

Finally hooked up my tach and the idle speed as suspected in pretty high
Posted by: limey222
Date: September 26, 2015 11:25AM

94 Camaro 3.4 V6 with FI. No apparent vacuum leaks. My doe speed is 1200rpm dropping to around 1000 when in gear with clutch in and brake on. Is this normal? Since there is no means to adjust to adjust idle speed (I understand it is fixed in factory) and can live with it if I have to. All of the sensors are new.


Moderator
Curtis Jacobson
Portland Oregon
(4576 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

authors avatar
Re: Finally hooked up my tach and the idle speed as suspected in pretty high
Posted by: Moderator
Date: September 26, 2015 01:46PM

Does your throttle body looks like this one?
http://www.tonkinonlineparts.com/images/parts/gm/fullsize/951020GM03-317.JPG

Have a closer look in the area around the big spring. On my MGB V8 I used an earlier Chevy V6 throttle body, and it actually does have a tiny little screw to limit exactly how shut the throttle butterfly can be. A quarter turn of that screw makes a big difference in idle speed.

Your engine computer moves an Idle Air Control valve's plunger in and out in tiny steps to precisely adjust RPM automatically as your engine warms up. (The IAC is #3 in the drawing above.) OEM engineers want engines to idle slowly to achieve low emissions and better fuel economy, and because slow is quieter. 1200rpm might be "normal" for your engine when it's first started on a cold day, but it's not normal in daily driving and it would get terribly tedious at stoplights. I expect a Chevy technician can adjust your programming. He'll probably adjust calibrations of your throttle position sensor (#6) and temperature sensors first.



Edited 1 time(s). Last edit at 09/26/2015 02:02PM by Moderator.


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