Need advice..Engine Knock

[TWITCH101]

So I bought a 01 yukon 150k from a friend and he told me the knock is normal out of these model trucks so I was like whatever you say I'll take your word for it.

Anyway the motor makes a knocking noise everytime it has a cold start....but after I let the thing idle for about a minute maybe less the knock will slowly go away and then the motor runs smooth. If I start the truck cold and drive it before the knock goes away then it sounds terrible (like a diesel or something) Other than that the engine is very strong, doesn't burn oil, and gets good gas mileage. Also it idles around 500 rpms when warm which seems a little low to me but it may have a chip or something. Its just that initial cold start after the thing has sat overnight that makes it knock. Its not bad while at idle while warming up but I would like to know what the cause is.
My first guess is that a knock sensor may be gone but I'm not throwing any codes on the dash so I don't know where to start.

Just hoping that someone on here has had the same issue or knows what I'm dealing with here.

Feel free to ask any questions if it may help....I'll answer to the best of my abiulities.

 

[07Burb]

This is commonly referred to as "piston slap" and, as your friend stated, is common with these models.

 

[TWITCH101]

This is commonly referred to as "piston slap" and, as your friend stated, is common with these models.

Is it anything to be worried about? should I have it fixed?

 

[07Burb]

Nope...nothing to be worried about at all. I would say that the vast majority of these LS based motors do it on cold start up just like yours does and they will run forever when properly maintained.

 

[TWITCH101]

Thats great....I figured it was alright since it ran smooth when warm but I just liked to know for peace of mind....i searched around online and found the same general consensus that you just gave me from other forums and mostly all said it was nothing to be worried about so I think I'll just keep driving it until I have a problem or make a discovery that could help fix it.

 

[GMC Yukon]

Yep thats the same sound I get after 180,000 miles that I put on her.... I Allways let it warm up and let the oil circulate befor driving her away. Cool starts suck... You mite want to put some good oil in her. I use Moble 1 full synthetic ( Truck & SUV ) Well worth the money! Mine has 237,000 on her now and still runs like a Time-X !

 

[TWITCH101]

I'm a synthetic fan as well as that is all I run in my motorcycle....I'll have to try it on my next oil change

 

[Kman]

YouTube Piston Slap.

Let the truck idle for a minute or two on cold mornings before you drive away.

 

[TWITCH101]

yea I always wait until the noise is gone before I drive...doesn't take any longer than 2 minutes tops.

 

[01HDtahoeNJN]

Not to Jack the the thread but in the winter/colder weather my engine makes a squeal like noise kinda like when a belt is wet...is that normal or okay?

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