2000 Toyota Corolla Hi I've got a persistent problem.

2000 TOYOTA COROLLA
140,000 MILES • 4 CYL • FWD • MANUAL
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KEVOCHEF
  • MEMBER
  • 2 POSTS
it all first started with engine codes p0300
p0301 and p0302 cylinders 1 and 2 misfiring,
when i got two new ones the code was only reading one cylinder misfiring so my mechanic changed it and it cleared he said when it came on again we would change the other. I moved away i still have the 2nd cylinder but now it is reading cylinder 1 and 2 again. Can the cylinder break that quick? should i get another one and replace both? It is also saying p0420 catalyst system efficiency below threshold bank 1. can the misfiring ciylinders cause this to come up?
Jul 7, 2009 at 5:15 AM
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MMPRINCE4000
  • ✓Experienced Mechanic
  • 8,548 POSTS
The P0420 code is a result of the misfire. Check plugs and coils, also run a compression test.

What did you replace to clear the codes?
Jul 8, 2009 at 12:38 AM
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KEVOCHEF
  • MEMBER
  • 2 POSTS
we changed one coil. and reset the light in hopes it would come back on to tell us which other coil to change.
Jul 8, 2009 at 4:06 AM
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MMPRINCE4000
  • ✓Experienced Mechanic
  • 8,548 POSTS
Check plugs also, they may be worn out if they have never been changed.

Also make sure the tube seals are not leaking oil into plug, it will also cause a miss.
Jul 9, 2009 at 2:24 AM
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