Hey I have a 2005 Chevy 3500 extended and I'm getting a knocking sound from somewhere under the hood. When I press the gas the knocking gets a little louder and faster

if the knock speeds up with rpm increase then it definitely is the engine. if it is a solid sounding knock that would be bottom end. if it is more of a hollow knock or more like a tick then could be top end...lifters, exhaust leak or check to see if anything is hitting your cooling fan.

Is it metalling sound ? if that's the case then don't drive it .. you might be having issues with connecting rod or the bearings in the both cases engine will seize. Consult a auto technician, but you wont have engine light on due to this.

If it is knocking due to misfire (which is mostly the case as the engine light is also on) .... than find which cylinder have the issue then clean or replace the spark plug. If you can get a scanner to read the car computer it will solve the issue in a blink. Otherwise start the engine ... open the hood .pull out spark plug connector one by one and notice the change in sound... the one that is bad will have no effect on the sound.

This could be anything from a loose belt to a blown rod. You need to have a mechanic check it.

there is a decal under the hood/engine compartment somewhere that the factory puts on that shows you the belt routing.

Look lines going to engine, gas regulator if is bad is leaking.

SMELL GAS YOU NEED CHECK ALL FUEL LINES UNDER THE HOOD IN THE ENGINE COMPARTMENT.IF GAS IS STRONG UNDER HOOD YOU DONT SEE LEAKING FUEL LINES.YOUR FUEL RAIL FUEL INJECTORS LEAKING OR FUEL PRESSURE REGULATOR O - RING OR DIAPHRAM LEAKING GAS.IF FIND NO LEAKS UNDER THE HOOD CHECK FUEL LINES UNDER CAR FROM ENGINE TO FUEL TANK FOR LEAKS.IF ALL IS GOOD YOUR EVAPORATIVE CANISTER SOAKED WITH GAS OR YOUR EMISSION EVAPORATIVE SYSTEM NOT WORKING. DEALERSHIP HAS TO CHECK AND FIX.

I had the same problem with my 2005 Trailblazer, thought it was the alternator so replaced it and it was still making that sound. It ended up being a $25 idler pully which took about 15min to change.

sounds like a steering column universal gone bad try shaking wheel while in park an look under hood at steering shaft

Sounds like you need a starter, or you have a loose wire somewhere under the hood.

SOUNDS LIKE A ROD KNOCK..ON THE BOTTOM END ... CHANGE THE OIL AND CHECK ITS CONDITION... SOUNDS LIKE U MAY HAVE A CAR WITH SOME MILES ON IT... TRY AN ADDITIVE OR USEING A THICKER OIL ..