Help me start diagnosing my Mazda Protege 2002, please!

[cartracer12]

P0421 should not be related to your dip in RPM unless the door in RPM is caused by a misfire. Intermittent misfires can cause the catalytic converter to fail prematurely. A lot of times if the catalytic converter is working marginally IE P0421 coming and going. A proper fuel injection service will clean out the cat enough to get its working properly again.

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[farcryNZ]

Hi Henry. I have an interest in these kinds of issues, with RPM dips etc.
If you go on the Mazda247 forum and search "alternator" in the protege are, there are a number of people who have posted with issues like this, that have been diagnosed successfully by their mechanic as the alternator.

I can not say for sure myself if this is the case for your car, but reading the posts of the problems these people had, it was a surprise to find that the alternator was the issue.


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[Henry]

Hi Henry. I have an interest in these kinds of issues, with RPM dips etc.
If you go on the Mazda247 forum and search "alternator" in the protege are, there are a number of people who have posted with issues like this, that have been diagnosed successfully by their mechanic as the alternator.

I can not say for sure myself if this is the case for your car, but reading the posts of the problems these people had, it was a surprise to find that the alternator was the issue.


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Hi, and thanks for the suggestion..

It could be the alternator since I've noticed that when the car is fully warmed up then I stop and start it few minutes later, the dashboard and all lights are a little dim, then I rev up to 1500 RPM and the lights get bright again..

I always thought this was normal behavior, or could it be something with the alternator?

[farcryNZ]

I don't know how to copy links from one tapatalk to another but on Mazda247
http://www.mazdas247.com/forum/showt...le-and-Misfire might work

Have a read of that, sounds similar


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