Low oil pressure on my 2011 5.3L, but wait!
 

Hi guys, I have a 2011 Yukon with the 5.3L. I have seen many posts about this and it seems like it can happen the same with a lot of people, or it can be different for a lot of people. I am one of those people. I have a low oil pressure issue, or so it seems like. The symptoms are after the engine is warm, and is driven around a little bit, my oil pressure drops to 18-19 psi, sometimes 20-21 if I’m lucky, and the idle is awful. I never get a check engine light or a code. The RPMs during idle fluctuate up and down between 400 and 600, and as it fluctuates you can feel a very noticeable thump coming from the engine. I do not have a lifter tick, and I also managed to disable DOD with a tuner, just to play it safe. I have replaced the oil pickup tube, the O-ring, changed oils and filters…..nothing. Changed spark plugs, wires, and coils….not it either. On normal acceleration, the oil pressure almost never passes 40, it goes as high as 38-39 but never any higher (unless the engine is cold). I was going to replace the little filter behind the oil sending unit, but for some reason I feel like it’s not that. The sensor does not seem to be the culprit either. I was debating on starting with the oil pump, but I have already dumped thousands of dollars into this car. I can’t exactly get rid of it because it’s financed for the next 4 years. I attached a video of it at idle, for reference. Any immediate advice would be appreciated.

Filter under the oil pressure sender being plugged is a common issue. Senders go bad also and verifying oil pressure with a mechanical gauge is needed.
Idle should never drop below 600, that's an issue. Even when A/C cycles it should not drop that low. Throttle body clean and carbon free ?
Full scan of all 4 code families is in order, that's step one in any shops diagnosis, not just looking for P codes.
For example my '11 LTZ has 41 readable modules in it that are all interconnected in the CAN system.
Without out a full range code scan to see what and any issues that are in there it's all a guess.

Check this video out for reference to what I’m talking about. When the oil pressure and RPMs dip, the entire car thumps. Haven’t checked the throttle body yet, but there might be an issue there as well as the car feels weak under acceleration. It definitely doesn’t have the glory it once had. I should also add the Yukon has a custom heavy duty bumper on the front, but I’ve had this problem way before the bumper was installed, it just wasn’t as bad.

If your oil sending unit isn't plugged or defective that an awful low oil PSI at idle 30 to 40 pounds is more normal.Repairman54 is probably correct about the filter under the oil sending unit. I've been working on vehicles for a long time and its almost always the sender, not the gauge that has issues. It's a bear getting to that sender on your vehicle, but it's not that hard if done right. Lots of great YouTube videos on this sender removal will show you how to do it more easily than I could explain here. Make sure your throttle body isn't defective or dirty as well. Might be a good idea to add Seafoam or Techron Complete into your gasoline tank as well.

Would the sending unit be causing the RPMs to fluctuate/make the engine thump at idle? I know I have to throw a scanner and real gauge on the car but my shop is closed until Monday.

Not likely. You may have a separate issue with that. I'd clean the MAF sensor and spray some cleaner into the throttle body and see if that makes a difference. I use contact cleaner on a MAF. It works just as well as MAF cleaner, and you can use it for many other things. Don't use carb cleaner as it leaves a residue, which is not good at all for a MAF. It's OK to use it on your throttle body, however.

Here’s a brief update. We decided to replace the throttle body completely. We cleaned the original one and tried to do a relearn, without plugging a device into the car. On top of idling way too high and it sticking before the idle goes back down to 500, it STILL idles rough. The RPMs fluctuate between 400 and 600, and the thump is still apparent. You can physically see the engine shaking when the hood is open. After replacing it, same thing, it sticks (probably needs a computerized relearn), and when it comes down to 500rpm, it still idles rough (fluctuates between 400-600), thumps every 5-6 seconds, and has a very sluggish acceleration. I should also add that there is a huge delay after pressing the throttle while driving. It’s like the engine doesn’t wanna go. My gas mileage has went way down after the throttle body work too. I’m out of ideas. Still no check engine light, and no lifter tick or anything.

anyone know what sensor this is next to my oil filter? 93 c1500
 

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Go on Rock Auto and look up oil pressure sender and knock sensor. They should have a picture of them.
Been a long time since I've had a motor of that vintage so I'm not fully sure.

Kenny Vick: Welcome to the forum. Next time start a new thread when changing the subject. That will assist someone searching for info. 😊