Crazyman1304

Hi all, I recently got a 03 silverado 1500 with the 5.3 vortec in it. When I got it it would not run for more than a couple seconds so I replaced the throttle body and now it runs and will idle if you let it sit for about 30 seconds but still trys to die if you put it in gear and go but thats beside the point. It's got a knock in what sounds like the bottom end but it had good oil pressure? Right 40 when it's idling and goes up when you give it some gas when it's in park. From what I know a spun bearing or something else in the bottom end would cause low oil pressure. It did throw a 02 sensor heater code too if that could have anything to do with it. Thanks for any help!

Gumby22

The rule of thumb for oil pressure is 10 PSI per 1,000 RPM, so if the oil pressure sensor is working correctly, it’s fine.

That being said, it’s always recommended to verify the oil pressure with a mechanical gauge if low pressure is a concern.

Keep in mind that sometimes noises can be deceiving, meaning that the source is isolated from the point where the sound is heard, but due to the way the engine/drivetrain is assembled, the noise is echoing/traveling and more audible in a different location.

Remove the serpentine belt(s) to rule out any pulleys and check the torque converter and starter mounting bolts for proper torque. A loose TC bolt can impact against parts of the bell housing, causing a knock; likewise, loose starter bolts can allow impact between the starter and flex plate gear.

It may also be helpful to remove the valve covers and inspect the rockers and push rods for obvious problems.

sk47

Hello; the 5.3 in that year range was sometimes prone to piston slap. The noise will go away as the engine warms up. Not a pleasant thing but not fatal to an engine. Had a neighbor whose engine i could hear from 75 feet when she first started it up. She had a lot of miles on that engine.