1997 Chevy Malibu Catalytic converter

1997 CHEVROLET MALIBU
100,658 MILES • 4 CYL • 2WD • AUTOMATIC
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NICOJR
  • MEMBER
  • 5 POSTS
How can I tell when I need to replace my Catalytic Converter? My engine light just came on so I changed my alternator but its still on. I went and got a diagnostics test and they came up with PO420 and PO108. When I start my car it makes a rattling noise under my car. Sounds like there is some kind of vaccum leak under my hood. I'm not sure which one it could be though. Can you please help me?
Dec 8, 2009 at 4:19 PM
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RASMATAZ
  • ✓Experienced Mechanic
  • 75,988 POSTS
The easiest test for converter plugging is done with a vacuum gauge. Connect the gauge to a source of intake vacuum on the intake manifold, carburetor or throttle body. Note the reading at idle, then raise and hold engine speed at 2,500. The needle will drop when you first open the throttle, but should then rise and stabilize. If the vacuum reading starts to drop, pressure may be backing up in the exhaust system.

Replacing it will not do you good till the caused is identified

P0108 MAP sensor problem
Dec 8, 2009 at 4:57 PM
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