Knocking/Valve Train Noise
My friend's 2007 Cobalt A/T recently began making what she described as a loud growl from the engine while she was out for a drive. While attempting to limp the car home, it apparently would stall at idle.
I took a look at it in the hopes it was something simple like a bad serpentine belt or seizing accessory pulley, but that whole assembly appears fine, although the serp belt is a bit worn.
The noise is a loud knocking from the cylinder head area that increases in pitch/intensity with engine rpm, and appears to be coming from every cylinder.
To me, it sounds like the timing is REALLY off and the engine is knocking. Engine had oil, and no idiot lights on. Going to run codes tonight, but in the mean time I thought I would ask the experts here what they think it might be.
Thanks in advance