Hello, posting my first questions.
Purchased first car in 30 years a week ago. (been a truck man)
Now have issues sooner than expected.
It's a 2003 Impala LS with 132,000 miles & 3.8
Motor.

Issues;
1. Severe squealing/ squeaking noise from engine which I cannot locate.
2. Removing oil filler cap stalls or shuts down motor unless removing slowly it keeps running & seems to ease squeal but still remains.

What I have done;
Changed tensioner pulley.
Changed PCV valve
Removed serpentine belt and started (still squeals)
Sprayed starting fld trying to locate vacuume leaks
At a loss!

Car runs great, accelerates, power is fine.
However did put machine on at auto zone & got a P0420 code. Light went off after new PCV valve.

Any input greatly appreciated.
Sorry the post wasn't a little longer.

 

P0420 is a catalytic converter code that it bit the dust or is plugged, Could be the source of your noise also.