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Discussion Starter · #1 ·
We have a 2015 Impala that my wife drives daily. Recently it's gotten to where it kinda stumbles/hesitates/shimmy's when you slow down behind a vehicle and apply throttle. Sometimes it does it from a stand still as well. I've hooked it to my scanner and it doesn't show any codes, any misfires, etc. I decided to try cleaning the throttle body and cleaned it best as I could. However, I noticed that the intake sucks vacuum through the threaded insert for the engine cover. I'm assuming that intake is bad, doesn't make sense why it would suck vacuum through a bolt hole but 馃し
This is the bolt I'm talking about....

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We have a 2015 Impala that my wife drives daily. Recently it's gotten to where it kinda stumbles/hesitates/shimmy's when you slow down behind a vehicle and apply throttle. Sometimes it does it from a stand still as well. I've hooked it to my scanner and it doesn't show any codes, any misfires, etc. I decided to try cleaning the throttle body and cleaned it best as I could. However, I noticed that the intake sucks vacuum through the threaded insert for the engine cover. I'm assuming that intake is bad, doesn't make sense why it would suck vacuum through a bolt hole but 馃し
This is the bolt I'm talking about....

View attachment 166560

The bolt head for my 2014 Impala 2LTZ (purchased new - original bolt) uses a T-30 socket to install / remove the bolt.

The bolt head in your picture looks like it is damaged, perhaps from overtightening?

If you are positive the hole is sucking air (how do you know?) - you may want to use high temperature epoxy to seal the hole and not use the bolt.
 

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Discussion Starter · #4 ·
The bolt head for my 2014 Impala 2LTZ (purchased new - original bolt) uses a T-30 socket to install / remove the bolt.

The bolt head in your picture looks like it is damaged, perhaps from overtightening?

If you are positive the hole is sucking air (how do you know?) - you may want to use high temperature epoxy to seal the hole and not use the bolt.

It's the bolt the dealer installed when we bought the car. It holds the engine cover on. I know it's pulling vacuum because you can hear it and when you cover the hole with your finger you can feel it. I put some silicone around it but didn't make a difference. I'll grab some starting fluid this afternoon and check the intake and hoses the best I can for a vacuum leak. If I can't find anything I'll let the dealer look at it and diagnose the issue because apparently I'm not smart enough to figure it out 馃槀
 

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The factory would have installed that for the engine cover, not the dealer.
 
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It's the bolt the dealer installed when we bought the car. It holds the engine cover on. I know it's pulling vacuum because you can hear it and when you cover the hole with your finger you can feel it. I put some silicone around it but didn't make a difference. I'll grab some starting fluid this afternoon and check the intake and hoses the best I can for a vacuum leak. If I can't find anything I'll let the dealer look at it and diagnose the issue because apparently I'm not smart enough to figure it out 馃槀

The dealer may have used an incorrect bolt and/or overtightened it then. The head looks damaged.

I would not use silicone, as it could be sucked into the intake system. If you want to seal it, use a high-temperature epoxy and do not reinstall the bolt.

Silicone can damage oxygen sensors.
 

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Dealer did. We purchased used and it didn't have the cover so they ordered one and installed it.

I looked closer at the bolt and cover on my 2014 Impala 2LTZ (3.6L). Under the bolt head, on top of the plastic cover bolt hole, is a rubber bushing (perhaps for sound or vibration control?).

If you dealer did not use this rubber bushing, even if they used the correct bolt, the bolt threads would reach too deep in the composite manifold (as the bushing acts also as a spacer) and probably damage the manifold as you describe.
 
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