Drop in oil pressure

[mtown27]

I posted this in the Hybrid forum but havent had any luck. Id imagine this also applies to non-hyrbid trucks as it is only an issue when the engine is running.

I've got a 2008 Hybrid Yukon with 190,000 miles on her. She's recently started to have oil pressure issues on the gauge dropping below 40 at idle, and RPM drops with a rough idle. I changed the oil pressure sensor and screen behind the motor in 2015. Sometimes the motor runs great all day, always going to Autostop at red lights and low speeds, and other times the oil pressure is always at or below 40 on the gauge. I did an oil change 500 miles ago with 5W-30. I'm stumped on what it could be. Engine seems to run better when the outdoor temp is below 85-90 degrees, anything over that and the oil pressure is an issue. Plugs are relatively new and clean. Oil pump going bad? I've seen others pull the pan. I've also seen someone post about a 2nd sensor on the side of the oil pan. The rough idle and not going to hybrid is eating me alive!! Any thoughts?

 

[JDC81]

synthetic oil or std? the oil may be thinning out too much in the heat if its regular.

 

[mtown27]

Synthetic. Im thinking about replacing the oil pump with the HV unit and changing the oil pickup tube o-ring. Will the weak oil pump cause the engine to shake a bit and run rough when the oil pressure drops low? I know the AFM is a huge issue with these motors.

 

[mtown27]

What's the range on the oil pressure for these trucks? I constantly run around 60, and when the truck runs poorly, at or less than 40. At start up it instantly goes to 60 and holds. Holds at 60 while I'm driving. When the temp outside is hot, the oil pressure drops to 40 or below and the motor runs poorly. At that point, the motor hesitate on acceleration and has a rough idle, sometimes a spike in RPM. See pictures below.

 

[mtown27]

Anyone have any advice on the random low oil pressure?

 

[swathdiver]

Not familiar with your motor, has it always run at 60? Are you the original owner? My 5.3 idles around 20 and is usually just north of 40 underway, all normal.

 

[mtown27]

2nd owner. I've had it almost 5 years and it's ALWAYS run at 60. Drops to 0 when it goes into auto-stop. Goes back to 60 during any drive or idle. Now it runs rough around 40 and won't go into auto-stop if it's around/below 40. It has a jerk/hesitation when it runs at 40 and at idle.

 

[swathdiver]

Well, hopefully someone familiar with your engine will chime in soon and help out.

 

[Danny3737]

It could possibly be a bad sending unit that starts to fail when it gets hot.

 

[mtown27]

Isn't the oil pump mechanical and not electrical? How hard is it to swap the oil pump?