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Slight knocking sound at idle

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Old Jul 10, 2014 | 08:15 PM
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Default Slight knocking sound at idle

Just noticed a few days ago a very slight knocking sound coming from the engine. It's more noticeable when I get under the car, and seems to fade when I get the car going

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Old Jul 10, 2014 | 08:39 PM
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hope you find it as I have been chasing that one for 3 years
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Old Jul 11, 2014 | 01:27 AM
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Default piston slap

Originally Posted by paloalto00
Just noticed a few days ago a very slight knocking sound coming from the engine. It's more noticeable when I get under the car, and seems to fade when I get the car going

View My Video
Sounds like piston slap. Had on my Trans Am & on my silverado. Google it !
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Old Jul 11, 2014 | 02:05 AM
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Originally Posted by warlock007
hope you find it as I have been chasing that one for 3 years
It seems like the sound goes away when I get the car moving. I'm hesitant to take it to the mechanic because it's $100 just for them to check it
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Old Jul 11, 2014 | 02:12 AM
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Originally Posted by Gaskill
Sounds like piston slap. Had on my Trans Am & on my silverado. Google it !
Just read up on it, turns out it's "normal" when you cold start the car. I guess that explains why the sound goes away once I get the car moving
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Old Jul 11, 2014 | 07:34 AM
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Turn everything off in the car and drive it to see if you still have the noise most prominant at 1000-1300 rpm.

If it's just the normal cold start that last about 2 minutes or so it's slap and that is normal for the ls1 motor, tho it shouldn't be. A lot of info on it, GM did different things with this motor than previous and post engines
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Old Jul 11, 2014 | 08:22 PM
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Originally Posted by warlock007
Turn everything off in the car and drive it to see if you still have the noise most prominant at 1000-1300 rpm.

If it's just the normal cold start that last about 2 minutes or so it's slap and that is normal for the ls1 motor, tho it shouldn't be. A lot of info on it, GM did different things with this motor than previous and post engines
I had A/C off and all that, I had a friend checking it and after a couple minutes he said "wait, I don't hear it anymore." So I'm guessing that's a good sign
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Old Jul 11, 2014 | 08:26 PM
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Then that would be the standard ls1 cold start piston slap and your ok
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Old Jul 13, 2014 | 12:01 PM
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Originally Posted by warlock007
Then that would be the standard ls1 cold start piston slap and your ok
My 03 Silverado and 04 Coupe have been doing it since day one !
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