3100 V6 Sounds Like A Sewing Machine

[RNJ]

I am at 176,000 miles on my GA. This noise is louder during acceleration. Engine temperature normal, no smoke or check engine light. Oil dipstick is clean. One Mechanic listened to the motor and said it's either a cracked piston, or rod bearing. I have driven 700 miles since then. The noise has not changed and can just barely be heard at idle. Any suggestions would be much appreciated.

 

[melsg5]

Did the mechanic try to isolate the noise to one particular cylinder by using a diagnostic tool to prevent cylinders from firing? You probably need a second opinion from a certified mechanic.

 

[CatSkinner]

Is it throwing any codes? It may have diagnostics that haven't lit the CEL. Also, a compression test mat be in order to confirm the first mechanic.

 

[GM Customer Service]

I am at 176,000 miles on my GA. This noise is louder during acceleration. Engine temperature normal, no smoke or check engine light. Oil dipstick is clean. One Mechanic listened to the motor and said it's either a cracked piston, or rod bearing. I have driven 700 miles since then. The noise has not changed and can just barely be heard at idle. Any suggestions would be much appreciated.

RNJ,
Are you still experiencing this issue with your vehicle? If you are I would recommend that you contact your local GM dealer and have them look into this for you. They may be in best position to get this issue diagnosed for you. Please keep me posted and if you have any questions please feel free to contact me anytime.
Thank you,
Stacy GM Customer Service

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[mtdad]

I had a similar issue in a suburban once. paid good money and the Certified mechanics told me I needed a new engine. Took it home and was working on something else when I saw insulation gone on o2 sensor where it had rubbed against some transfer case wiring. When I separated and reinsulated the connections, the engine smoothed right out. Seems the short initiated the anti knock sensor which retarded the timing. Then replaced the o2 sensor. That problem fixed 3 or more years ago.