Loud engine knock sounds like theconnecting rods in a 3.5L v-6 2002 trooper

knocking or clanging usually means engine rebuild or replacement
What is piston rod knock Engine Knocking Yahoo Video Search Results 3 Causes of Engine Knock

Something inside engine broke

Loud knocking is usually a "bad sign". If water got into the engine, and you tried to start it, you could have bent or broken rods. That's a major engine repair.

Not sure on model but to me sounds like its a dodgey valve lifter when the seals start to go they cannot hold the oil and when there under pressure they basically empty them selves hence when you turn the engine off and restart you get a rattle sound untill the valve fills again as long as the cars running ok leave it untill you have to replace them unless there easy to do sone are sone are a pain

I agree it sounds like a rod knocking but don't worry it want knock long!
Gillight

If you are hearing a loud "knock" and it is coming from the bottom of the engine you probably have a bad crankshaft bearing(s) which means engine rebuild or replacement.

loud knocking is usually a piston problem[wrist pin-piston-piston rings -rod bent damaged-crank -bearing ]piston hitting valve pull plugs and check for fouling it will narrow down area do compression test but knock usually doesnt last long before engine usually goes south other which u can hope for and can sound like a knock would be the exhaust gasket good luck

it means that you need to research either a different car, or a different engine for this car. A loud knocking noise indicates a connecting rod is loose, and your engine has little to no time left before the rod or endcap breaks, completely messing up your engine, and making it very difficult to change. If you must drive it, drive it slow, and be super gentle with the gas...like you're driving on ice. If it's more of a ticking noise, that could be a lifter, but a loud hollow sounding knock is a rod. You may also have a check engine light showing up on the dash from the knock sensor.

lifters tick and noise is upper end of engine if lifters are making noise could be from a bad valve,bad lifter ,push rod ,oil pressure,rocker arm - need to take do compression test find out if valve problem and which cylinder is problem also take off valve cover and check for proper oiling of valve head and look to see if and are damaged or loose-------a knocking sound usually comes from lower end of engine,rod knock etc.and thats usually rebuild of engine

you have a ROD knock,,,,the oil level can be good and compression can be good,but the bearing on the rod to crank is shot and now has too much play and is causing excessive play and noise,soon the rod will come out the block and seize the engine,,if its knocking that loud then its too late to fix it,,your gonna have to replace the engine really soon,,,sorry but its normal of the dohc engine to do this usually between 90 to 130k miles they let loose but the single cam dont have this issue