Hi. I have got a 2015 Suburban LT. It has got almost 55,000 miles.
Last week the engine started vibrating and i could see the RPM went down to 500 when on N and 350-400 when on D idling. And the oil pressure shows 20 on idle and barely 40 when drive. After all of these issues i can feel a strong vibration of the engine and a clicky noise .

I have taken the car to a dealer and they told me there could be a misfire but the check engine light never came on. So they perfomed throttle body maintenance and injection cleaning. I have paid $261.00 but tue issue is still the same. The technician told me there was nothing they could do since there was no code on OBD...

I went a local garage and have replaced the spark plugs with the cables and the air and cabin filters and oil and the oil filter for sure.

The result is a big NOTHING !!!

And I don't know what to do where to go!!!

Thanks in advance for your responds

 

I'm not familiar with these specific motors, however I think you're on the right track with respect to troubleshooting.

If the surging isn't related to spark generation (plugs, wires, coils) I'd look towards air (MAF/MAP), fueling (pressure/flow) and timing (cam sensor/crank sensor) to see where the issue lies.