Inifiniti, engine knocking

My Infiniti I30, 2000 model, has been great for so many years. I got 245,000 miles on it and seems that it will go for another 245000. But, since last 15 days, I can feel a distinct knock from the bottom of the car ( it feels so). This happens after about 30 minutes of driving and I can feel and hear the knock when the car is stopped at a light or stop sign. The sound comes like every few seconds at uneven pace. I cannot hear it when car is moving. My mechanic changed the Air intake sensor ( pretty expensive) but the problem still persists. I put super unleaded and also STP engine treatment. The problem continues. Car is working fine otherwise. Any comments and or suggestions

I have no idea why the mechanic would change an Air Intake sensor because that would have nothing to do with a knock at all.

Usually a knock down low points to rod bearing wear. (Serious as it gets)
Given the age, mileage, and down low knock if the car were mine I’d run an oil pressure test on it with the engine hot and determine if excessive engine wear has finally arrived.

About 6 months ago, low oil pressure warning sign did come on. That was some faulty sensor and when replaced, the warning sign went away. But suggestion will be acted up tomorrow. I love this car.

The sensor referred to in this case would be the oil pressure sending unit and without knowing the tiniest of details the low oil pressure lamp could have pointed to a serious issue other than the sending unit.
Low would actually be a misnomer because when an oil light illuminates this means no oil pressure, not low.

Given the age and mileage the oil pressure should have been checked at the time the sender was replaced and this makes me wonder about other things such as whether the oil level was at the FULL mark when this even happened, whether there could be engine oil sludging present, etc, etc.

Unlikely, but consider that to some people the description of a true engine knock and a heat shield may sound the same to some people.

Let your wife out of the trunk!!!


Edit: Sorry…I couldn’t resist…I tried…failed miserably.

Thanks for the laugh Chassos.

To the OP: OK4450 has been inside more engines than most of us have ever seen. His advice on this I agree with 100%.

Using a higher weight oil can sometimes help squeeze some extra life out of a worn out engine, but there’s no real inexpensive “fix”.