Intermitent kocking

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Dec 12, 2008 | 11:09 AM

Heidi

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7th Gear

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Intermitent kocking

I have a 1996 Silver Edition Corvette, LT4 automatic with 90,000 miles. I have the car regularly serviced and is in excellent condition. Yesterday, when I started the car I heard an intermittent clicking/low knocking sound. There is no grinding when I start the car and all fluid levels are where they should be. It is more persistent on lower RPMs and when the car idles and gets muffled on higher RPS. There is no spark misfire. It sounds like perhaps a bearing problem??? I initially thought it may be the catalytic converter. The rocker arms/pistons look fine when I removed the head covers. The computer module in the car shows no malfunctions. Without tearing down the engine I am looking for any suggestions. It has been difficult trouble shooting this problem and any suggestions would be appreciated!! Thank you!!

Dec 12, 2008 | 11:30 AM

Jake Dragon

Racer

Joined: Nov 2008

Posts: 309

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From: Lakeland Florida

Does it change with the RPM or is it a steady knock that is just there.
My alternator went out on me and made a knock like sound, it went away with some screeching and smoke

You can use a long metal rod placed on your ear, move the other end around on the block and it will act like a stethoscope and tell you where the knock is coming from.
Or you could just get a stechoscope

Dec 12, 2008 | 11:41 AM

Heidi

Thread Starter

7th Gear

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Jake, I have used a stethscope but have had touble locking the knock. It sounds somewhat like the engine metals contracting after you turn it off. Not so much knocking I guess more of a popping noise.

Dec 12, 2008 | 12:36 PM

rick lambert

Le Mans Master

Joined: Oct 2003

Posts: 6,130

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From: seattle WA

Maybe you should get another friend to help isolate where it's coming from. How are the oil and coolant temps, and oil pressure? Kinda wondering if you're not getting some detonation from unburnt fuel in the cat, since you mentioned the cat. That might cause a popping sound.

Dec 12, 2008 | 12:37 PM

69mako

Race Director

Joined: Jan 2000

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From: USA. Northern Virginia

Could be a lifter going bad

Dec 12, 2008 | 01:00 PM

Heidi

Thread Starter

7th Gear

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This may sound stupid but approximately 2 days prior to hearing the noise I bought gas at Arco. Usually I buy my gas from from Exxon or Mobile. I don't know whethere this would be a possibility

Dec 12, 2008 | 01:01 PM

Heidi

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7th Gear

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Rick, this may sound stupid but approximately 2 days prior to hearing the noise I bought gas at Arco. Usually I buy my gas from from Exxon or Mobile. I don't know whethere this would be a possibility

Dec 12, 2008 | 02:49 PM

Jake Dragon

Racer

Joined: Nov 2008

Posts: 309

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From: Lakeland Florida

Does it get louder and harder under load? If you put it in drive and hold the brake you should be able to tell.

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Dec 12, 2008 | 02:54 PM

rick lambert

Le Mans Master

Joined: Oct 2003

Posts: 6,130

Likes: 2

From: seattle WA

Now I wonder about the gas, co-incidence maye, maybe not. You maybe hearing pinging (or knock) if I were you I'd probably find an octane booster and try that, can't harm.