2002 Mazda 626 Misfire/warm up catalyst

Tiny
D8652T
  • MEMBER
  • 2002 MAZDA 626
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 94,000 MILES
I'm getting a P0300 and P0421 code on my 626. If I'm reading the book correctly the P0300 says Random/Multiple Cylinder Misfire detected and the P0421 says Warm Up Catalyst Below Threshold (Bank 1). Can you tell me what these codes mean and just what I need to do to correct them? The car starts hard and my son says it stinks. It is still getting 22 to 23 mpg but, I think it can do better. I appreciate any help you can give me and would be happy to donate after confirmation of problem. Thanks
Saturday, February 9th, 2008 AT 10:08 PM

1 Reply

Tiny
BLACKOP555
  • MECHANIC
  • 10,386 POSTS
The warm up catalyist is probably having problems due to unburned gas by the missfire code.

For the missfire since it is random it will be hard to diagnose.

First thing to do is check for bright blue spark on all cylinders, they should be well defined, post back what you find.
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Sunday, February 10th, 2008 AT 7:16 AM

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