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5.3 spark knock question

5.3 spark knock question

Postby wolfy692005 [OP] » Apr 12 2013, 11:53pm

Hi there, I am new to the forum and new to the 5.3.. I'm an old school check guy and know my way around the old motors.
I have a bone stock (well except the muffler) 2000 Silverado 4x4 z71. I have owned it since it had K in the ticker and the dealer salesman was driving it,
it now had K on the ticker. the problem is spark knock or at least that is what I think it is.. it had lost power over the years but it still gets up and goes. it knocks under a load and especially if you are tooling along and it shifts into say overdrive at a lower speed loading it.. when I bought the truck I never did it. over the years I guess it has gotten worse. I first noticed it while pulling heavy trailers.. now it is every day. I have always used "junk" gas in it and if you use premium it doesn't do it near as much, but who can afford that?
I use the truck every day driving 70 miles to and from work.. I just don't want to hurt the poor tired engine..
it also has a rear main seal leak that is not really bad yet but I am sure some day soon it will need to be fixed.
thanks for any advice.
Roy
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Re: 5.3 spark knock question

Postby jocko463 » Apr 14 2013, 4:12am

Roy,

First thing comes to mind is a bad knock sensor (or two). Computer is not supposed to allow the engine to knock continuously ...providing it senses it's knocking. Computer will tweak timing to run the engine right on the edge of knock. And a fried sensor will probably set a code ...

Another thing that pops up is your EGR valve and the EGR port. The more modern EGR valves are controlled by servo motors ...much more accurate than intake vacuum. Modern engines need the EGR feedback exhaust to reduce combustion temps for emissions reasons and to prevent knock. If the valve has quit it should trip a code. If the valve works okay but the EGR port is clogged with combustion deposits you might not be getting the proper amount of recirc exhaust.

And that brings us to "junk" gas. A steady diet of fuel that is not "top tier" rated will allow all manner of combustion deposits to form both in the cylinders and intake track. The old girl could probably stand a good upper intake and fuel injector cleaning. You shouldn't have to buy premium grade fuel for your truck. And the price difference between the "junk" gas and "top tier" fuel might be a buck or two per tankful ...least it is in my area. Absolutely no incentive to run my truck on the cheap stuff when it costs just about the same as the real stuff.

Mike
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Re: 5.3 spark knock question

Postby MikesZ71 » Apr 14 2013, 5:48am

I would also point my finger at the knock sensor(s). My 04 had the same symptoms. If I jumped on the gas, I would hear a pretty good amount of knock, and it drove me nuts. Never once did it set a check engine light, but knocked like crazy. I got on Amazon, and they had a package deal on there....intake gasket, and both knock sensors for the same amount that auto zone wanted just for the gaskets. And it was all AC delco. Did the job, and didnt have any more issues. If you end up having to change the knock sensors, its a fairy easy job. just took time. Good luck with it!
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