Persistent Knock Problem - 2000 Tahoe - HELP!!

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SmokeEater2

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I'm fresh out of ideas on what to try to resolve this knock I have in my 2000 Tahoe 5.3L w/ 58,000 miles. As far as I know, everything is dead stock with no mods.

It seems to knock on hard acceleration and also when I pick up the throttle after "coasting" at high way speeds. If I keep the same throttle position, the knock will quiet down until I provide additional throttle. I do not get knock if I'm in neutral (ran up to 2,000 RPM).

No MIL or codes. No problems starting and smooth at idle. Minor piston slap for first 30-45 seconds on cold start.

Here's what I've tried:

- Replace both knock sensors w/ AC Delco 213-3521
- Replace knock sensor harness w/ Dorman 917033
- Replace intake gaskets w/ AC Delco (teal colored) & new intake bolts
- Replace fuel filter w/ AC Delco ACP GF652
- Replace EGR Valve w/ AC Delco 214-1080 & AC Delco gasket
- Replace spark plugs w/ AC Delco 41-110 Factory gapped
- Replace PCV valve w/ Purolator Part # PV1063

I have Seafoamed it using 1/3 can into brake booster, 1/3 can into fuel. I have run 3 bottles of Techron (two 10oz on full tank with Sunoco 87 & one 10oz with 10 gallons of Shell V-Power 93).

Changed oil to Mobil 1 with PureOne filter. Small amount of minor particles on drain plug magnet. There was a small sliver of metal in oil filter, but I'm pretty sure it came from the oil filter case when I cut it open.

Smoke tested it looking for vacuum leaks. Fixed mis-seated air intake on throttle body that was leaking.

As you can see, I've spent a small fortune on parts and time, so I'm looking for some advise.

Attached are picts of the original plugs - they look good to me, but I'm not an expert plug reader.

I've also included an OBDII log using a OBDLink SX 2.0 by ScanTool. Timing advance seems way too advanced to me. Not sure what else could be causing it.

Help!!
 

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BlackZ-HO

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as dumb as it sounds i had the same problem and put about 1000 into it trying to figure it out, turns out my passaneger side front shock was broken, the top mouth broke off and it was bouncing around making a knocking noise while it hit metal, once i put in new ones the noise was gone.
 

ScottyBoy

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Have a helper rev the engine to at least 2500 RPMs while you closely stare at the AC belt. Look at it from under the truck for a better view if you need to. Make sure the AC is on high when you do this. If the AC belt flails wildly above 2000 RPMs and the belt tensioner is jumping around, there is your problem. My AC compressor on my 01 went out and that's what it did. The compressor starts locking up causing the belt and tensioner to flail around. The belt tensioner was what was making the knocking sound. And my AC still blew ice cold during all this, but then it broke 3 belt tensioners before I gave up and replaced the compressor. It turns out that 00-04 compressors have this known defect, yet GM only issued a tech service bulletin about it and not a recall.
 
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SmokeEater2

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Thanks for the suggestions. Both shocks are in good shape. I'll take a look at the AC Belt as suggested, but it only happens when in drive. If I'm moving at 65 MPH and I pop it into neutral and bring RPM's up to 2000, no knock / ping. I also don't get the knock or ping when I power brake.

Anyone have thoughts on the high timing advance in the odb logs? The two seem to be related, but I'm not sure and I'm uncertain how to fix.

Thanks again for the input.
 

chevyboy831

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unless the noise is very obvious that its coming from the bottom end of the engine, these 5.3's are also knows for the lifters to fail. ive seen cams get flatten. id get the lifters checked and cross my fingers for it not to be an engine.
 
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