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Discussion Starter #1
Hey guys,
Just wanted to get some advice from everyone. I just bought a 2005 envoy Denali xl in new perfect condition on the body. The engine holds oil pressure but then slowly losses pressure as the car idles. But then the oil pressure goes back up when the vehicle is revved up. It takes a few minutes for the pressure to fall so I think it’s a oil pump. It also needs a transmission rebuild because it only has 1 and reverse.

I have a l33 engine to replace the engine that I was keeping as a spare for my Camaro but now I’m thinking about using it to replace the engine that has lost the oil pressure. I’m putting in new bearings and freshening up the l33.

So I was trying to figure out which engine is in my Denali and the 8th digit of the vin is a M which indicates a LH6. The LH6 is a gen 4 engine but I was under the impression that the gen 4 engines didn’t come out until after 07. I know the l33 is definitely a gen 3 but I know I can’t just throw a gen 3 engine into a gen 4 vehicle without swapping the crank and some other things. Or buying the converter box.
I just would like to know if this would be a direct swap or if I should just replace the oil pump and put the same engine back in. Thanks in advance!
 

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Your taking a huge leap, swapping engines.
What pressure are you seeing on the Envoy engine?
Did you use a proper oil pressure gauge?
Did you change the oil and filter, what did you use?

Just me, but if you do have a leaking oil pump, that's a lot less work that an engine swap.
 

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Discussion Starter #3
Yes, I changed the oil and filter and there is no change.

The problem is that the engine slowly loses oil pressure as it idles. Once the engine is revved up it gets it’s oil pressure back. This does not happen every time though. There are sometimes when I can idle for 20 minutes and not lose any oil pressure. I’m using the stock gauge on the car. The oil pressure will literally drop down to zero if I let it. The engine also has some broken manifold bolts that I figured would be easier to addressed with the engine out of the vehicle. I definitely would rather not pull the engine if I don’t have to and save the l33 for my Camaro.
Thanks for the reply and the insight. It is much appreciated
 
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