Knocking noise

REDBANDIT72

MEMBER
1996 CHEVROLET TAHOE
5.7L
6 CYL
4WD
AUTOMATIC
280,000 MILES

I have a vortec engine and so far after troubleshooting, I have changed distributor cap, fuel pump, fuel filter, oil, oil filter, spider injector an set timing, after all that it is knocking. Can anyone please help? I am up into the thousands and I need my truck fixed.

She will turn over, but will not stay running for long she blows a lot of smoke. I am afraid I blew up my engine or at the very least blew the head gasket.

Thanks, Lisa

7 Replies

JOHNNY G.JR

MECHANIC
320 POSTS

What color smoke is she emitting? Whitish is normally head gasket. Try a compression test on cylinders or a cylinder leak down test.

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Sunday, January 1st, 2017 AT 9:19 PM

REDBANDIT72

MEMBER
3 POSTS

Goes white and blue. She idles so rough, and if I get on it after a few seconds will backfire.

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Sunday, January 1st, 2017 AT 9:24 PM

JOHNNY G.JR

MECHANIC
320 POSTS

Blue smoke is oil burning, not good possible bad piston rings, worn valve guides or seals. Have timing checked again. Might have jumped a tooth.

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Sunday, January 1st, 2017 AT 9:52 PM

MHPAUTOS

MECHANIC
31,937 POSTS

Not sounding well at all, I agree. Check that the valve timing is correct and do that compression test, but I feel that it is at the end of its life.

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Monday, January 2nd, 2017 AT 2:34 AM

KEN L

MASTER CERTIFIED MECHANIC
47,513 POSTS

Hey Lisa,

Lets do a compression test first and while you are at it check for a blown head gasket.

Here are a couple of guides to help you.

https://www.2carpros.com/articles/how-to-test-engine-compression

and

https://www.2carpros.com/articles/head-gasket-blown-test

This will guide us in the right direction

Please get back to us

Best, Ken