2007 Avalanche Low Oil Pressure at Idle

[jhall0828]

The oil pressure on my 2007 Avalanche with 108k miles (LC9 Flex Fuel 5.3L with AFM) is low at hot idle (less than 20 psi per dash guage). It comes back up just off idle, but even at highway speeds is only hovers around 45-50 psi. Previous history on the truck is at 80k miles I had the AFM Oil Pressure Relief Valve Deflector installed due to oil consumption and oil fouled plugs on AFM cylinders. At 90K miles, I had the cam, lifters, push rods, rocker arms, etc. replaced due to knocking on cold start along with continued high oil consumption. I noticed the lower idle oil pressure after getting the truck back after the cam, etc, replacement. The oil consumption has remained higher than what I would expect, and recently I had an extremely rough idle/miss. I pulled the #1 plug and the insulator was cracked and oil appeared to be leaking through the plug. Any thoughts on what problems may be contributing to the low oil pressure, oil consumption, etc.?

[Doug_Scott]

Have oil pressure checked with a known good mechanical gauge. Oil lights used to come when pressure dropped below 7psi when I was a mechanic at a Plymouth/Chrysler dealership, can't think it would be much different with other of the big 3.

 

Oil is not going to leak down the insulator into the cylinder. You would be seeing combustion gases coming out of the insulator before a thick liquid could leak through it. Assuming that you meant you though oil was leaking in via the insulator. That being said,(and if you discount the AFM causing it) if you are seeing the plug as being oil fouled, then it looks like you have found out where the oil is being consumed. Now you need to figure out if it is bad guides, or scratched cylinder bore, or seized oil control rings. Nice thing about internal combustion engines is that there are a very limited number of ways to get oil in a cylinder. Bad thing about that only one of those ways is cheap to fix. Doubt it is valve seals though.