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Old 09-19-2009, 04:40 PM   #1
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Default knock sensor corrosion?

Put another manifold on today and it seems my hissing on the highway at load in 4th has gone away. So I assume I cured some sort of air leak. Anyways, at WOT I'm still getting the damn 8 degrees of KR. I'm fed up and about ready to find a new hobby. While I was there I did happen to peak at the front knock sensor and see it corroded and some on the wall too. I couldnt see the rear sensor. Can this cause knock like I'm getting? I dont hear a DAMN THING like knock at WOT. I apologize for the poor pictures (Iphone)



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Old 09-19-2009, 06:59 PM   #2
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replace them. yes they could be causing your problem. esp if your not hearing any knock.
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Old 09-19-2009, 07:56 PM   #3
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I would replace them both. I just replaced both on my 01. my front looked fine my rear looked x50 worse than yours. I also had about 1/8" of water and rust sitting in the cavity of the rear. I sealed the top boot with high temp rtv. to keep the water from getting back in.
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Old 09-19-2009, 07:59 PM   #4
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I did not visualize the rear sensor. From what I've read it's usually much worse than the front sensor so I expect mine to be the same. $90 for the sensors from SDPC
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Old 09-19-2009, 08:03 PM   #5
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Either way you're eventually going to have to replace them and build a dam with RTV (there's a TSB in reference to knock sensors corroding, check it out on your AllData). It makes sense that the knock sensors could be sending false signals considering how corroded they get. I *think* that there's a sub-harness to the sensors that you'll probably want to replace also.
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Old 09-19-2009, 08:05 PM   #6
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Why would I need to replace the harness?
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Old 09-19-2009, 08:18 PM   #7
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Just do like me and disable the knock sensors. For every knock I have it pull zero degree of timing. If it's knocking you'll hear it. Who needs a PCM to tell you what to do?
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Old 09-19-2009, 08:20 PM   #8
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Quote:
Originally Posted by hirdlej View Post
Just do like me and disable the knock sensors. For every knock I have it pull zero degree of timing. If it's knocking you'll hear it. Who needs a PCM to tell you what to do?
Hmm, I'd be a little weary of doing that just incase it is indeed knocking. You'd think that with 8 degrees of KR I'd hear something but I know there is knock that isn't audible sometimes.
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Old 09-19-2009, 08:27 PM   #9
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People drove cars for years without knock sensors and they never blew up. I have a hard time letting the computer control certain things that I don't wish for it to control. Such as disabling the IAT spark tables and anything else spark related that's not coming directly from the spark table. If it's 150 degrees out or 150 below, I want to be in charge of the spark tables, not the PCM. I'm old school I guess......
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Old 09-19-2009, 08:28 PM   #10
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They also had much better gas then too.

I always run shell 93, but still I think it's questionable.

I'm debating running some race gas when my tank gets low and see if I still have the same KR. If so then we know what the problem is.
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1500, 1999, corosion, corroded, corrosion, gmc, knock, location, lower, lq9, sdpc, sensor, sierra, silverado, voltage

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