Catalytic converter?

Tiny
KOALAHUGS
  • MEMBER
  • 2009 GMC ACADIA
  • 6 CYL
  • AUTOMATIC
  • 369 MILES
My engine light is on and after using an
ODB? Tool I was told I need a catalytic converter. There were also code for misfiring on all the cylinders. I was told the problem with the misfiring needs to be fixed before replacing the converter.
Wouldn’t a faulty catalytic converter cause misfiring?
Thursday, November 28th, 2024 AT 7:42 AM

3 Replies

Tiny
STEVE W.
  • MECHANIC
  • 13,576 POSTS
The misfiring dumps raw fuel into the exhaust, which is what can destroy them because they actually get too hot, and it damages the ceramic inside them. As such the misfires need to be repaired first. Then you would replace the converters. The only way a converter causes misfires is if it is plugged enough to restrict the exhaust flow. That would also cause other problems. If it was showing a P0300 but no individual cylinder codes, then I would look at the fuel system first. Low fuel pressure would cause a lean condition that would show as misfires.
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Thursday, November 28th, 2024 AT 10:42 AM
Tiny
KOALAHUGS
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Thank you for a prompt answer. Would changing the spark plugs/tuneup help with the misfires?
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Thursday, November 28th, 2024 AT 1:45 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,576 POSTS
It might, but it depends on what the real cause is. You say it has multiple misfires, correct? That means it randomly misfires in different cylinders at different times. That is why I suggest the fuel system as the first start. It can alter all of the cylinders. The ignition system, however, has 6 plugs, 6 coils, and 6 injectors. To get a P0300 means that all 6 of a given item started to fail at the same time. What are the chances of all of one item just suddenly failing all at the same time? However low (or high) fuel pressure, or an intake air leak (brake booster, broken vacuum line or intake gaskets all would affect all 6 cylinders.
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Thursday, November 28th, 2024 AT 8:23 PM

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