Update: I did the oil pump replacement, o-ring and oil relief valve as well. Melling Hi-Volume and Hi-Pressure.

Before the repairs: cold idle was at 40, hot idle was 10 and driving hot was between 30-40 depending on the rpms
After the repairs: cold idle is at 70, hot idle is at 20 and driving hot is between 40-70 depending on the rpms

Whats concerning is how fast the pressure drops to that hot 20 when coming to a stop. I feel as if there is still an issue somewhere in the engine cause the hot idle was always at a good 25 up until the last 20k miles... at 185k now.

if I give an xtra 100 rpms at hot idle, i get an instant jump to a good 25. So now my question is..... how can i get the ecm to change its idle by an extra 100 rpms?????? what do I need to get this to happen?

 

Nothing wrong with 20 psi at idle; it is adequate/acceptable for that motor

 

I have heard that 20 is okay... after what I have seen in the last 6 months or so makes me extra cautious with the oil pressure. Maybe i will run 10w-40 in the summer instead of the 10w-30 year round. I have a 10w-30 full synthetic in it now after the fix and plan on doing a flush oil change within a week or so. Would be an interesting test to see the hot idle with 40 weight

 

so during the 5 day 90+ heat wave this past week, my hot idle is creeping under 20 with 30 weight oil.. I was ok with 20 psi but under makes me unsure considering all the work I did to try and eliminate this low idle oil pressure. I am sure the engine is fine at 17/18 psi on idle but I am the kinda DYI guy that has to know WHY. I have seen a post on cam bearings creeping out and another claiming its the valley cover. I DO NOT have the solenoid based AFM valley cover because I did a AFM delete repair 5 yrs ago with cam change (its now basically the same engine out of the factory as the 07 Hummer 5.3)... can't imagine what a basic valley cover would do to idle oil pressure. I did try my best to look up from under the engine to see if I can see any cam bearings walking there way out but cant say that I saw them all.

I will drop some 40 weight oil in soon and let you all know if a 90 degree day gives me back my 20psi hot idle

 

I have a 2007 Suburban with 325,000 miles. It sits at or above 20 psi at idle. I've only run Mobil 1 since I got it with 7,000 miles. I've had low oil pressure on the gauge a few times over the years. checking with an external pressure gauge always shows proper pressure so the engine internals are fine. I found a TSB regarding the oil filter possibly being the issue after replacing the pressure sensor and still showing low oil pressure. Replaced the oil filter and pressure was back up to over 20 psi at idle. The other times it was the oil pressure sensor. The screen in the hole under the pressure sensor has never been clogged. Just bad sensors.

 

Screen never clogged because you have always used a synth. oil.
Regular oil no matter the brand gunks up those screens. Synth. is well worth a few extra bucks IMO.

 

so my final post on this low hot idle oil pressure issue....

I did the oil change as I said... Mobil 1 full synthetic 10w-40.... previous oil was synthetic 10w-30 after the oil pump install (also a correction to my cold or high rpm oil pressure... its maxed at 60 psi, not 70 in a previous reply)

My now current Hot idle oil pressure on 10w-40 has risen by about 3-4 psi compared to the 10w-30. Hard to be precise on the numbers as the gauge has 20 psi tic marks... 20 - 40 - 60 - 80. I am happy with a steady hot idle of 20 psi and will end my repairs at this (I hope) and close this chapter of the GM 5.3 high mileage low oil pressure mystery.

Thanks to all for your inputs!