2000 Mazda 626 LX Manual trans with Check engine light ON

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Aceh^Texas - 03 Oct 2006 04:18 GMT

HI folks,
A week ago, at night under heavy rains, I got trouble on the highway
when the spark plug suddenly failed, the engine rumbled and the check
engine light was on. The engine stopped and couldn't be started until 5
minutes. The engine eventually started and with 40 Mph I got home. The
next day I replaced the spark plugs, and also the wires. The check
engine light then OFF, the engine runs smoothly, until the CEL suddenly
came ON again while I was commuting in town. My mileage is still 93 K.
Can anyone tell me what's wrong and how to get rid off this CEL? Can I
turn off the CEL by disconnecting the negative battery and hold the
pedal brake for 10 second? Will it work on 2000 Mazda 626? Thanks in
advance.

Ace

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halatos@gmail.com - 03 Oct 2006 16:34 GMT

> engine light then OFF, the engine runs smoothly, until the CEL suddenly
> came ON again while I was commuting in town. My mileage is still 93 K.
> Can anyone tell me what's wrong and how to get rid off this CEL? Can I
> turn off the CEL by disconnecting the negative battery and hold the
> pedal brake for 10 second? Will it work on 2000 Mazda 626? Thanks in
> advance.

Without the current OBD-II diagnostic code(s) there isn't anything we
can do to diagnose your problem. Run the car down to your local
autozone and have them hook their scanner up to the car. Record the
codes(it will be FIVE characters..a letter and four numbers) and come
back and post it here.

Chris

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Aceh^Texas - 03 Oct 2006 17:51 GMT

I went to Autozone, they scanned my car and came with the following
codes:

P0420
P0304

They told me that it is regarding catalyst system eficiency and
cylinder misfiring. Please tell me how to fix it. Thanks

> > engine light then OFF, the engine runs smoothly, until the CEL suddenly
> > came ON again while I was commuting in town. My mileage is still 93 K.
[quoted text clipped - 10 lines]
>
> Chris

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thetoolman - 03 Oct 2006 19:23 GMT

> I went to Autozone, they scanned my car and came with the following
> codes:
[quoted text clipped - 4 lines]
> They told me that it is regarding catalyst system eficiency and
> cylinder misfiring. Please tell me how to fix it. Thanks

P0304 = #4 cylinder misfire! Fix this and see if P0420 go's
away...P0420 Catalyst system below threshold (bank one) !

You may have a bad NEW plug (has happened before) or you damaged the
plug wire for #4 when you pulled it off to change plugs....Fix the
misfire then drive the car on the highway for about 30 miles or so,( to
get the CAT hot) go back to Autozone and have them clear the codes
after the fix, if the CEL comes back on with the P0420 the CAT. may
have gone south because it was borderline anyway and the misfire drove
it over the edge

HTH, Rick

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halatos@gmail.com - 05 Oct 2006 16:21 GMT

> P0420
> P0304
>
> They told me that it is regarding catalyst system eficiency and
> cylinder misfiring. Please tell me how to fix it. Thanks

Wow...I bet the check engine light was -flashing- at you wasn't it. :)

You need to identify and repair the problem with cylinder #4. Then
disconnect the battery and drive the car for at least 3 cold starts to
see if you have also burned out the cat. Hopefully it will be okay once
you fix the misfire and stop dumping raw fuel into it. If the check
engine light does not come back on after repairing the #4 misfire give
yourself a pat on the back. If it does come back on you may wind up
replacing the cat(read:$$) but if your area does not do emission
testing you could leave it as-is and put some electrical tape over the
light.

Good luck with it.

Chris

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Aceh^Texas - 08 Oct 2006 07:30 GMT

Thanks for your advices.

I check the cylinder #4 and the wire. Then I went to mufler shop to
check the exhaust system, cause even after I changed the spark plug #4
that died recently, I heard kind of rattling sound underneath the
vehicle. Somewhere in the middle, especially in the morning when I
start the car, and when I release the gas pedal.
The guy at the mufler shop checked everything under the vehicle and
found that the cat is broken. When he hammered around the cat, it
sounded "krk krk krk" inside the cat. He told me that the ceramic
inside the cat has torn a part. And if I continue to drive in this
condition, the broken ceramic may clog my exhaust or engine.
Then I made quick decision to replace the cat. I choosed 'Magnaflow'
performance cat. The part and installation cost me about $200 plus
$9.99 tax. After that I reset the Check engine light and drove for 15
miles on the highway at 70 Mph. The check engine light doesn't come
back.

Ace

> > P0420
> > P0304
[quoted text clipped - 17 lines]
>
> Chris

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