flashing check engine light

[rakf1]

I have a 96 mazda protege, Recently the check engine light came on, actually started flashing first and then stayed ON. It happened just after I started driving in the morning after it had been parked on a rainy day. The car stuttered while the light was flashing.
I had a similar problem 6 months back, driving on a rainy day. I got tune up to fix it.
Can anyone tell me what might be the reason for the light to come ON after a rainy day...
The car runs fine now, just had that stuttering on rainy day, otherwise it drives smoothly.
Also let me know how I can reset the light ?

[drdisque]

to clear it on some cars all you have to do is disconnect the battery, on other cars you need a code reader to clear it.

My guess is that water is getting into a wiring harness and causing one of the voltages to the ECU to read out-of-spec.

[RandomTask]

Could be a transmission issue. There could be a faulty signal coming from a sensor, being computer controlled, it tries to lock it into gear, causing the stuttering. (I've had a mazda with the same problem before, the speedometer sensor was faulty, causing the same problem)

If the actual motor was studdering, then an ECU issue, perhaps a misfire. Best take it to the dealer, they'll be able to pin point the issue fairly quickly. Best of luck

[curtis73]

1996 is OBD2, which means this: When the check engine light comes on (CEL) it means, "golly, partner. You're possibly polluting the atmosphere cause somethin ain't right." When you get the flashing CEL it means, "You'd better figure this s#!t out before you damage something."

Basically the solid light is a way to get you to spend money at the dealership, and it stays on a long time even if the problem goes away. The flashing light is potentially serious stuff depending on what it is.

Listen to RandomTask. Check some tranny connectors and stuff first on the Mazda. If the light continues to flash, stop by a major parts store chain like Auto Zone, Kragen, or Advance. They offer free diagnostics. Just go in and tell them you need your OBD2 codes read. They can advise you after that.

[rakf1]

I just went to Autozone and got free diagnostic(thanks curtis73) , It was misfire in cylinder 4.
Like I told, I had a similar problem 6 months back on rainy day, and so I got tune-up that time.
So I'm thinking its not the spark plug or wires.
Any idea what would cause misfire in a cylinder bcoz of rain.

[383PhoenixAm]

If the wires are old it could be possible that water is conducting energy between wires, causing crossfire (or whatever they call it now).

[curtis73]

Many things can cause misfires, including MAF/MAP, low compression in that cylinder, O2 sensors, cats, you name it. The computer registers something about a misfire and it probably just picked it up in cylinder four.

Given the fact that it just rained, have the code cleared and drive it. If it comes back, have it re-read. If it doesn't come back, it was probably just water in the ignition somewhere. You can help this by putting a little dielectric grease in the boots of the wires (both ends) and making sure the rest of the ignition system is in top condition. Just 'cause its new doesn't mean its right.