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2007 chevy
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56 Posts
Discussion Starter · #1 ·
i am cleaning the throttle body but noticed that the butterfly from the throttle stays partially open. is this normal? is it supposed to be fully shut? it stays open maybe a few milimeters. i can push it with my fingers and to close it but then it goes back to its place. i thought that this had to be fully closed but never had a TBSS before so just wondering if this is normal on these trucks
 

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2003 gmc envoy_slt
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7,190 Posts
Is it open with the power disconnected? Does it close completely if you turn the key on without starting the engine?
 

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2005 chevy trailblazer_lt
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1,339 Posts
Don't force it. And I don't think you should even move it with the battery hooked up - or wires to the TB not disconnected.

I think there is always a small gap. Even at idle, it still needs air.
 

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2002 chevy trailblazer_ls
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139 Posts
just to be sure grab a flat head and some pliers and force it to be fully shut........................................................................................
..................jk please dont really its all good in the neighborhood
 

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I finally found information about cleaning a DBW TB. I don't know if this applies to the GM TB but the one featured appears similar. When the TB throat and butterfly are clean there is a small gap between the edge of the butterfly and the throat that allows a minimum air flow for the idle mixture when the butterfly is fully closed. The butterfly is controlled by a stepper motor and it should not be forced to move by hand (or flathead and pliers:hissy:). The PCM controls the stepper motor and when the TB gets gunky the PCM opens the butterfly to provide the correct idle mixture air. That may be why the butterfly is now slightly off completely closed. When you clean the TB the battery is disconnected and the ignition is off and the key should be removed. When the job is complete and the engine is started the PCM resets and the stepper motor should close the butterfly to adjust for the cleaned TB. There is only so much adjustment the PCM can compensate for a dirty TB and then at that point poor engine operation begins.
 
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