Unidentified noise

**maxoverdrive2** · 12-11-2008, 04:45 AM

Greetings Ladies and Gents,

I have a problem that hopefully someone can help me with. I have a 2001 Z28 with 61,000 miles on the clock (I've had it for about 5 1/2years), that has developed a noise that I can not identify. No....it's not the typical lifter noise that is so common with the LS engines (although I have that too), but rather, it is a hollow noise that increases with RPM. I have taken the car to several dealers, but no one has been able to fix it. I have a feeling that if I walked into the dealer with money falling out of my pockets, instead of an extended warranty policy..........the problem would have been solved long ago. The power is way down on the top end probably by 20%, however, the mileage is about the same......325 or a little more per tank. I drive the car daily, and I only get down on it occassionally. The only thing that I can think of at this point is wrist pin noise. Can anyone tell me what that sounds like and some of the characteristics that go along with it. Could the coils cause this? Thanks in advance for any insight that you may offer........Maxoverdrive.

**bills98ta** · 12-11-2008, 01:15 PM

Maybe pull the vavle covers, rocker assemblys, and push rods to check them. Could be a bent push rod. That's about as deep as you can go, with out a magor tear down.

**side2000** · 12-11-2008, 01:27 PM

if it's under warranty (and you know motor is covered) run it hard and break it. the infamous ls1 noise is actually not lifters, it's the piston slap. so if you are experiencing a new "tick" then a collapsed lifter is your most likely candidate. wrist pin's usually sound like a "knock" more than a "tick". the phrase "hollow noise" leads me to believe it's not a lifter, and it is internal. as bill said, pull valve cover and scope to see if your valvetrain is loose, if not then beat it up til warranty gets you new motor. . . .

**slp1122** · 12-11-2008, 01:32 PM

Originally Posted by side2000

if it's under warranty (and you know motor is covered) run it hard and break it. the infamous ls1 noise is actually not lifters, it's the piston slap. so if you are experiencing a new "tick" then a collapsed lifter is your most likely candidate. wrist pin's usually sound like a "knock" more than a "tick". the phrase "hollow noise" leads me to believe it's not a lifter, and it is internal. as bill said, pull valve cover and scope to see if your valvetrain is loose, if not then beat it up til warranty gets you new motor. . . .

did you seriously just tell him to break his motor so warranty will fix it?

**side2000** · 12-11-2008, 01:47 PM

he said hes got a warranty, if motor is covered and problem is not in his valvetrain, then yes. i'm serious. he can definately insure that his motor is covered before he does so. it's either that or start diggin in his own pockets.

**maxoverdrive2** · 12-12-2008, 05:26 AM

Mornin Guys.

Thanks for your responses. I replaced the push rods approx. one week ago hoping that I would find a bent one..............none found. With regard to "piston slap"...........yeah, it might be. The hollow noise that I previously described sounds very similar to a rod knock but without the metallic noise, and not as solid. If anyone is familiar with a loose harmonic balancer on an old small block.......that's what it feels like (but not nearly as violent) when the car is at highway speeds. I checked the driveshaft to see if it was bent or missing any weights. I checked the front pulleys,etc; everything was good. I even checked for bent wheels or lateral run-out on my tires; all good. I then realized that the noise and vibration still occurs when the vehicle was not moving. It doesn't seem to matter whether the engine is under load or not. The reason I Imentioned the possibility of bad coil(s) is because it definately has a miss that intensifies with increased rpm. At idle an intermittent miss is felt through the shifter (6 speed), and the seat. Yeah.... I thought about trying to "break it", but it kinda goes against how I try to live and what I believe in. If I did that, I would be no better than those rip off artists who I've read about who will take your money for goods that they have no intention of delivering (please understand that I'm not judging.........because I really appreciate ALL of you responses). By the way......kudos to those who report "rip off artists" on this site........lets continue to watch each others back! If you guys can think of anything else with regard to my ailing car I would appreciate you input. Thanks..........MAX.

**juiced99ws6** · 12-12-2008, 03:42 PM

Have you thrown any codes? If you missfiring then you should have a code to point you in the right direction. No need to wait for a light either, it will only throw the light if the problem is reported consistanly. I know your problem is consistant but hell, it might just not be getting picked up as such by your ECU. You could also ohm out your plug wires and check your plugs to make sure you are firing ok and not running lean.

My guess on your losing power top end is that whatever is knocking is knocking harder at increased RPMs and is tripping your knock sensors and retarding your timing. You can go to a speed shop and have them do a little datalogging for you.

**maxoverdrive2** · 12-15-2008, 04:45 AM

Mornin,.......Plug wires are relatively new, as well as the plugs. I was real careful not to crack the insulation on the plugs during installation. I did get a check engine light the other day for about 15 seconds, but it never appeared again. I'm going to take your advice and see if I can't get some data logging done bucause I think there could be something to the knock sensors being activated. The roughness of the engine is definately enough to trigger them.
Thanks for your input.