If a knock sensor goes bad ................ - ZR-1 Net Registry Forums

carter200 · 09-01-2010

Will or can there be an audible knocking sound (like a bad rod bearing) that can be easily heard? Just curious, thanks

rhipsher · 09-01-2010

Do you hear a knocking sound?

carter200 · 09-01-2010

Quote:

Originally Posted by rhipsher

Do you hear a knocking sound?

Yep and it's a loud one

rhipsher · 09-01-2010

Quote:

Originally Posted by carter200

Yep and it's a loud one

Oh sheet! Might be a bad lifter but if i's really loud then maybe a rod bearing P.Med you.

Kb7tif · 09-01-2010

On my 92 a complete main bearing set was installed (motor was pulled) Still had a knock not a tap a deep lower knock. Crank or connecting rod culprit.

Aurora40 · 09-01-2010

Just a peanut gallery two cents. But I believe the knock sensor is tuned somewhat specifically (via a crystal with a certain resonant frequency? Or at least that's what I thought) to the tune of a ringing block. I don't know if clunky noises will necessarily affect it.

I do believe though that the ECM will advance the timing to a point where it expects knock, as a self-test of the sensor. If it didn't see a knock signal, it will set code 43. It won't run the test if it sees knock signals before it gets around to running the test.

So if your knock sensor is MIA, it should throw a code.

Also, there's practically no way you should have knock at idle or low throttle. The cylinder pressures are really low. So if you hear it all the time, I wouldn't think it is spark knock.

carter200 · 09-01-2010

Thanks for the thoughts guys. Anything else that might cause a knocking sound besides rods and crank in an LT5?

A26B · 09-02-2010

Dual mass flywheel commonly sounds like a rod knock at idle when it gets "worn". if you advance the rpm to 1,000~1250, hold it steady & the knock goes away, it's probably the flywheel.

If the knock is not present at the higher rpm, you may have a weak miss. You might consider new plugs or gapping closer at about ).040"~0.042". Demps favors the closer gap on the later cars, I'm on the rail whether that's a good move.

The real problem is probably the Dunn heads. I have a real nice pair of 90 Birmal heads that I would trade with you, being the good ol boy I am! You know how we Okies take care of our neighbors to the south.

carter200 · 09-02-2010

Jerry,
I bet you do have a set of Birmals for the far superior DUNNs but the knock problem is NOT my car. My 95 purrs like a kitten

I have received news on the possible cause of the knock and will let the owner speak after checking it out.
Good to know my friends to the North are so thoughtful

Z51JEFF · 09-02-2010

A dead cylinder will cause the knock from the flywheel.I got this with dead injectors,dead coil.Carter,hows my TB plate coming along?

09-01-2010	#1
carter200 Join Date: Jun 2004 Location: Texas Posts: 2,431	If a knock sensor goes bad ................ Will or can there be an audible knocking sound (like a bad rod bearing) that can be easily heard? Just curious, thanks

09-01-2010	#2
rhipsher Join Date: Aug 2008 Location: Houston 90 Red ZR-1 Posts: 2,320	Re: If a knock sensor goes bad ................ Do you hear a knocking sound?

09-01-2010	#5
Kb7tif Join Date: May 2009 Location: S Nevada Posts: 352	Re: If a knock sensor goes bad ................ On my 92 a complete main bearing set was installed (motor was pulled) Still had a knock not a tap a deep lower knock. Crank or connecting rod culprit. __________________ 1995 Convertible Supercharged Auto 1974 454 550hp (avatar car) On the blocks- -Scharger install ! 1992-Zr-1 Sold. Watson Headers Ported Plenum, Housings Random tech cats Fidanza Flywheel Chipped, Relocated Mat Woods 165 stat Borlas, Straights 1996 Lt4 Sold 1994 Lt1 Sold 2004 Z06 Sold AKA** Illenema

09-01-2010	#6
Aurora40 Join Date: May 2005 Location: Leesburg, VA Posts: 2,713	Re: If a knock sensor goes bad ................ Just a peanut gallery two cents. But I believe the knock sensor is tuned somewhat specifically (via a crystal with a certain resonant frequency? Or at least that's what I thought) to the tune of a ringing block. I don't know if clunky noises will necessarily affect it. I do believe though that the ECM will advance the timing to a point where it expects knock, as a self-test of the sensor. If it didn't see a knock signal, it will set code 43. It won't run the test if it sees knock signals before it gets around to running the test. So if your knock sensor is MIA, it should throw a code. Also, there's practically no way you should have knock at idle or low throttle. The cylinder pressures are really low. So if you hear it all the time, I wouldn't think it is spark knock. __________________ Bob Saveland Former owner of #2517 [IMG]http://a.random-image.net/aurora40/vette.jpg[/img]

09-01-2010	#7
carter200 Join Date: Jun 2004 Location: Texas Posts: 2,431	Re: If a knock sensor goes bad ................ Thanks for the thoughts guys. Anything else that might cause a knocking sound besides rods and crank in an LT5?

09-02-2010	#8
A26B Join Date: Dec 2003 Location: Arcadia,OK Posts: 3,373	Re: If a knock sensor goes bad ................ Dual mass flywheel commonly sounds like a rod knock at idle when it gets "worn". if you advance the rpm to 1,000~1250, hold it steady & the knock goes away, it's probably the flywheel. If the knock is not present at the higher rpm, you may have a weak miss. You might consider new plugs or gapping closer at about ).040"~0.042". Demps favors the closer gap on the later cars, I'm on the rail whether that's a good move. The real problem is probably the Dunn heads. I have a real nice pair of 90 Birmal heads that I would trade with you, being the good ol boy I am! You know how we Okies take care of our neighbors to the south. __________________ Jerry Downey JERRYS LT5 GASKETS & PARTS http://www.jerrysgaskets.com 1994 *ZR-1*, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc. 2016 Black-Red, 3LT-Z51 Auto 8-speed.

09-02-2010	#10
Z51JEFF Join Date: Dec 2007 Location: Fremont,Ca Posts: 3,038	Re: If a knock sensor goes bad ................ A dead cylinder will cause the knock from the flywheel.I got this with dead injectors,dead coil.Carter,hows my TB plate coming along?