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I have read on the forum about cabon knock in the N* motor. Indeed, when I bought the car it had some cold carbon knock that pretty much goes away when operating temp. is reached. That knock is still present. I had my oil changed at the dealer 500 miles ago. I noticed today when I rolled the window down at the bank that when the motor is warmed up there is a metallic knock that comes on just above idle under a load. The noise goes away at higher speeds, >1300rpm. If you rev the engine lightly the knock comes and then diminishes as speed stabilizes, and disappears if you let off the gas. At idle, the noise is barely there. Sounds like a rod bearing. My concern, is that the noise seems to be load related. Call me paranoid, some of you might remember my story aboout how the car was returned with a coolant leak, dead battery, and filthy beyond belief. I wonder if the tech drained the oil out and then started the engine without adding new oil. The oil light does not flicker but that doesn't mean anything. I am not going to drive the car until I know more. What do you guys think?
 

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One way to check for a rod bearing is to put the engine under load and disconnect the plug wires one at a time. If the noise goes away on a particular cyl. then that should be the bad boy.You don't mention the milage but given the year of the car it very well could be carbon knock.If u go to an auto parts store u can buy a stethascope for around $5 .Listen to the engine...u will be able to till if the engine noise is coming from the top or bottom.The north* is really packed in the compartment but u can soon tell where the noise is coming from.
I just tore my engine down because of a burnt exhaust valve and found 5 of the cyl. packed solid with carbon....check the easy things first.I believe u will have to pull the engine to get to the con rods and that will be expensive any way u do it....good luck
 
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