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cabmando cabmando is offline
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Join Date: Jul 2013
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Originally Posted by javadog View Post
First, quit starting and driving the damn thing. If you've got what you think is a rod knock, an oil analysis is useless. Pull the pan and look at the rod end. If you have excess clearance, pray that the crank journal isn't ruined. If you see that the rod end or crank journal is darker than the others, that is a sign that excess heat was involved and I'd suggest you look for an oiling problem. If you end up pulling the motor apart, check that cylinder's piston top for detonation signs.

Examining the cat will tell you if it failed from heat. That's usually from excess raw fuel in the exhaust.

The two problems may or may not be related but the cat failure was probably a result, not a cause.

I should probably mention that the oil viscosity that should be used is dependent upon the designed bearing clearances, so it's possible that one of the bearing clearances wasn't right to start out with, or maybe the wrong weight of oil was used at some point.
Not driving it. It's at the dealer. But you might be onto how I can prevent this from happening again... just stop driving it.

If it's over fueling an oil analysis will show this.

Can't examine the cat, it's a part of the manifold so the only way to view the top side is cut it apart from the manifold.

The two problems are definitely related. The short block has 9000 miles on it and didn't make a knocking sound before the cat plugged up.

5w20 is what goes in the car and it gets changed at shorter intervals than the manufacturer recommends.
Old 09-03-2020, 10:59 AM
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