Please help! …. What is this tap/knock noise?!

[Bender9406]

I just picked up a 14 Sierra 5.3, and it only makes this noise once it’s warmed up? Has anyone heard this before?? It does not sound good. 

[Supreme Pizza]

Someone tapping a ballpoint pen against the fender?

[JimCost2014]

1 hour ago, Bender9406 said:

I just picked up a 14 Sierra 5.3, and it only makes this noise once it’s warmed up? Has anyone heard this before?? It does not sound good. 

FullSizeRender.mov

Welcome to the site.

 

Your link does not work, so do you have access to the service records?

 

Wondering if the vacuum pump has ever been replaced? Maybe a lifter has collapsed? Just guesses.

[Supreme Pizza]

The audio file (video) works for me. Sounds like someone whacking a pen against a fender. Try plying the audio file with a different browser.

[Bender9406]

I’m so sorry … I uploaded from my iPhone. I will try and get something better uploaded.

[CamGTP]

Does it get louder with rpm?

[JimCost2014]

26 minutes ago, Bender9406 said:

I’m so sorry … I uploaded from my iPhone. I will try and get something better uploaded.

No worries, the more info you can provide means you will get much better answers. Some very knowledgeable people on the site that can help.

[Bender9406]

https://drive.google.com/file/d/1_7mOY251Z7tJBQeOSBZDkZMjNCdfNOKL
 

here is a link to the video … does that help? 
 

Thanks Jim for being so kind. 
 

And I’m unsure about rpm’s. I’ve always been at idle/park when noticed. 

[Bender9406]

1 hour ago, Supreme Pizza said:

 

 

[Bender9406]

https://drive.google.com/file/d/1vO8ojl2bpotXkoedAmKTQt5VHnkNbJas/view?usp=drivesdk
 

here is an mp4. ^^

[JimCost2014]

14 minutes ago, Bender9406 said:

Thanks Jim for being so kind.

You are very welcome, time of year when we should all be extra nice to each other

[Supreme Pizza]

Oh. Well that seems like a misfire. Unburnt fuel combusting in the exhaust. If this is true, then it would probably only happen when the engine is warmed up. The hot exhaust ignites the unburt fuel. The muffler hides the backfire sound.

 

If this is true, then you should be getting codes for a single cylinder misfire, or multiple cylinder misfire, and possibly some O2 sensor codes.

 

The auto parts store can scan the computer and give you the codes for free.

Edited December 25, 2021 by Supreme Pizza

[JimCost2014]

5 minutes ago, Bender9406 said:

https://drive.google.com/file/d/1vO8ojl2bpotXkoedAmKTQt5VHnkNbJas/view?usp=drivesdk
 

here is an mp4. ^^

Do you have a scanner, or access to one?

 

Taking you do not have a constant CEL on the dash, wondering if there are codes stored and someone tried clearing them before you bought it.

 

That sounds nowhere normal in any way.

[Bender9406]

I have a scanner and can see what it says when I plug it in. I’ve never seen a CEL come on but maybe something is stored?
 

I do only hear it once it’s warmed up.

 

if it’s misfire and unburnt fuel I assume a coil and/or spark plugs should take care of that?

[Supreme Pizza]

If you can get a code that pinpoints a particular cylinder, then you can move the spark plug, spark plug wire, and coil to the next cylinder. Then you clear the codes and drive it. Then re-scan the computer. If the misfire code follows the part to the next cylinder, then its an ignition problem. If the code stays with the same cylinder, then you have a compression or injector problem. Don't start replacing parts until you know what to replace. I do these kind of diagnostics all the time.