"Chirp" at Low RPM + Knock
 

I have been hearing this random chirping sound like a squeaky wheel for quite a while now. I happens infrequently at idle, but when it happens it is always followed by a drop in RPM... maybe 200 RPM. When I give it a tiny amount of gas, it squeaks repeatedly, maybe 5-6 times rapid fire as the RPMs fall, then goes back to intermittent random squeaks as described above. It also squeaks rapid-fire as the RPMs fall off when I shut the motor off.

I thought it was an exhaust leak at the band clamps until today. I spent a bunch of time with red silicone sealing up the band clamps. I let it run for a while and slid under the car, and there is a knock coming from the passenger side of the engine. The driver's side is quiet... just normal valvetrain noise. I can hear it best through the headers from under the car. It's very faint above the car. The knock definitely follows engine RPM.

The last issue I have had for a long time is a misfire-like situation. If I leave TC on and gun it, the car will fall on its face. No codes, no TC warning on the DIC, no nothing. Just a slight pop and no power. I always drive with TC off because of this. Now I'm starting to wonder if it's related.

So my question is... what engine problems can cause chirps as RPMs fall past ~650 or when the motor shuts down? Whatever it is also seems to be causing a light knock and perhaps a misfire with TC on. I'm supposed to drive to the lake in 2 days, so I'm short on time to get this figured out.

Here is a video that happens to have captured some of the chirping. It does it at 32 seconds (random idle version) then you can hear it flutter after each rev, then again on shutdown at the end.

I'll try and get a video of the knock tonight if I can slip my camera under there without overwhelming its microphone.

Well.... that sounds way to familiar.... I'm gonna bet you have a stuck lifter. I just had the exact same situation, misfire, chirping and knock. I had a lifter stuck in the #1 cylinder. I have a video of mine on here somewhere.... I'll post the link.

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Here is what mine sounded like.


https://www.youtube.com/watch?v=wcSH...e_gdata_player

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Man I hope you're wrong. I don't recognize the sounds in your video, but my initial suspicion was a lifter problem. I imagined it more like the roller going out on me though. I really don't care what it is as long as I find it before it destroys my engine! I might have enough time to pull valve covers before I'm supposed to drive this car 5 hours to the lake. I need to come up with a backup plan in case we decide I shouldn't drive it that far.

Basically I couldn't tell where mine was coming from... it sound like it was in the top of the motor and I removed my valve covers... everything was good.

Chevy dealership pulled the heads and bingo. Lifter was stuck and wore down the first lobe on my cam... so they replaced the lifters and new cam.

Theres a TSB on this.... take it to the dealer.

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After watching some more videos of stuck lifters... I just don't think that's what it is. The knock is nowhere near that prevalent. Mine is an LS3 too... I think the TSB is for L99 lifters.

::EDIT::

And I trust the dealer to figure it out about as far as I can throw them. They can have my car for warranty work when I can tell them exactly what is wrong.

::double edit::

And I did come up with a contingency plan to drive another car this weekend. So it can sit safely and wait for me to have more time to check things out.

A bad roller on a lifter will sound about like a belt squeak.

Theres also a lifter failure TSB for LS3s... It was found when mine stuck. I have a custom grind cam so I needed some support to have mine warrantied.

Mine started sounding like a belt squeak and then went onto knocking somewhat...



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Well.. you guys could be on to something. I grabbed a video. You can hear the passenger side tapping and the driver's side doesn't make the same noise. I really think the chirp sounds like a roller. It really reminds me of a ball bearing that is going bad. I don't really know at this point though. Thank you guys for chiming in. I need all the leads I can get.

thahemp,

Sincere apologies to hear about the sound you're experiencing. I understand you don't have much time to have it inspected, but I would recommend taking it to a certified GM dealership when you do. I would be more than happy to set up a visit and monitor the process for you. Feel free to send me a PM regarding this matter.

William R.
Chevrolet Customer Care

Dang.... its hard to tell by the video... but mine started as a squeal and would go away then it squealed constantly and then onto to squealing and knocking...

All that happened over like a week... and I spent most of that trying to figure out where it was coming from.

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Thanks. I'll take it to my dealer when I figure out what the problem is. Until then, I'm going to leave it parked to keep anything from getting out of control. I have to make sure it isn't something I caused first. I'm sure you can appreciate that.

Yeah... mine is different. It has been doing this for a LONG time. I only noticed the knock after putting headers on... not surprisingly. Headers are like a stethoscope into your motor! You might still be right and it's the lifter body squeaking against its bore or something like that. I'm trying to keep an open mind.