knocking noise

hello everybody, I got a 97 tahoe 5.7 liter 4x4 that has recently begun making a knocking noise. I can hear it a little after I start it up but quickly fades away. Also when it revs down the engine will make a low winding sound accompanied with the knocking sound. I can't seem to hear the noises when it idles...mostly when I'm speeding up or slowing down. any advice would help, thanks.

hello everybody, I got a 97 tahoe 5.7 liter 4x4 that has recently begun making a knocking noise. I can hear it a little after I start it up but quickly fades away. Also when it revs down the engine will make a low winding sound accompanied with the knocking sound. I can't seem to hear the noises when it idles...mostly when I'm speeding up or slowing down. any advice would help, thanks.


what oil viscosity do you use...manufacturer ? mileage ?
this may be the piston[s]..is the engine condition good ? how often do you replace the engine oil/filter ?

check the PCV hoses for leaks..

the engine has 180,300 miles on it give or take 100 miles but still runs strong, good acceleration and passing power. oil has been changed on average every 3000 miles or about every 4 months using recommended factory weight, conventional 5w30 oil. Last tune-up was around January of 2009. Replaced plugs, cap and rotor, transmission oil/filter, wires and fuel filter. never had any problems what so ever until just recently (noise). Mostly city driving with the exception of after semester trips back home from school. Don't know if this matters but I live in higher altitudes (7000 feet) where our winters get rather cold and last longer then where I previously lived.

I would try using about 5oz of marvel mystry oil in the crankcase oil..see if in a few start ups it goes away..if so it is carbon deposits..

check for spark plugs and other ignition componets that need replacing..it is possible a poor spark is causing the carbon issues..

if the problem don't go away it then is very possible the engine is being to go...