2002 envoy rattle knock?

[warriorpluto]

This is the one I got from an auction. The noise goes away at anything over 560rpm. Before I run it back through the auction, what do you think this noise is? Sounds almost valve train related. I also know the 02 is prone to piston skirt failure. I drove this all the way from the auction. Noise is there basically only at idle. I replaced the oil and no change in sound. Would a bad flywheel make this noise?

 

[gmcman]

Disconnect one coil pack harness at a time and see if the noise changes. May throw a code, may not but it's something to try.

 

[dkvasnicka]

Couldn't a dying VVT solenoid cause this?

 

[gmcman]

Sounded louder below.

If killing 1 cyl at a time doesn't show anything, I would next take a look at the flex plate for cracking as well as the bolts to the torque converter.

 

[Mooseman]

As soon as you said it stops above idle, I would have said the timing chain tensioner but listening to it, it's too regular and is louder lower down. See if you can feel the knocking on the valve cover at the oil fill cap.

 

[warriorpluto]

Ok I didn't have a chance to try the things you guys mentioned today but I will get right on it tomorrow and see. What does unplugging the coil pack supposed to do? Will knocking stop if on a specific cylinder?

 

[gmcman]

Unplugging one coil will remove the force applied to the piston/rod from combustion. Sometimes a rod bearing noise will dimish slightly or mostly from not having this load applied to the rod bearings. Have someone listen below and see of the noise changes or stays the same with the same intensity.

You may hear the noise go from a slight sharp rap to a lower pitched rap or thud.

The fact it goes away above idle could be a lash adjuster, timing chain, hard to say without being there...or possibly a rod bearing from low oil pressure at idle, which goes away slightly with increased oil preasure.

Rod bearings sometimes are a little more quiet when cold then get more pronounced when warmed up....this is in the early stages though, may not be the case here.