I finally found this on the internet. looks like it may be a widespread, but fixable problem with the 2.4L engine & others. I am kind of ticked off that GM has not sent out a formal letter to all of the owners of the vehicles involved. Bulletin reads as follows:
#PIP4716A: Sharp Engine Rattle Noise At Start Up - (Feb 10, 2011)
Subject: Sharp Engine Rattle Noise At Start Up
Models: 2011 Buick Regal
2010-2011 Buick LaCrosse
2009-2010
Chevrolet Cobalt
2010-2011 Chevrolet Equinox
2009-2011 Chevrolet HHR
2009-2011 Chevrolet Malibu
2010-2011
GMC Terrain
2009-2010 Pontiac G5
2009-2010 Pontiac G6
2009-2010 Pontiac Solstice
2009-2010 Saturn Aura
2009-2010 Saturn Sky
2009-2010 Saturn Vue Equipped with the following engines
2009-2010 2.0L (RPO LNF)
2009-2011 2.2L (RPO LAP/LE8)
2009-2011 2.4L (RPO LE5/LE9/LAT/LAF)
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This PI was superseded to update models, years. Please discard PIP4716.
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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
In rare instances a technician may comment they hear a short, sharp rattle noise from the front of the engine on start up.
Recommendation/Instructions:
If the noise is from the front accessory drive area, inspect the engine belt. We have seen concerns with engine belts causing a loud ticking type noise. If found, verify power steering pulley outer edge is aligned flush with shaft and repair as needed. If pulley alignment is correct replace the engine belt.
If the noise is still present and is very short and sharp in duration (2-5 seconds). This may be an issue with the cam phasers not parking properly. Once the noise is verified as the phasers, they must be replaced. If the cam phasers are replaced, remove the CMP actuator solenoids to inspect for debris. If debris is found clean and inspect for torn or loose screens and replace if necessary.
Note: If debris is found in the solenoids and phasers change the oil and filter before returning to service, in some instances it may be necessary to change the oil/filter multiple times with a test drivein between each. The filter and solenoids can be inspected afterwards to ensure no additional debris is present.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.