Hi, so I've had my 2003MP since May. The first few months, it ran great. And every so often the CEL would come on steady and then turn off by itself. My dad's mechanic friend replaced the spark plugs...I would say...2-3 months ago?

I believe a few months ago, I was driving long distance (half an hour away on highways) and when I was at 55mph, the car sputtered and slowed down to the 40smph. The CEL was blinking for a few minutes and then turned steady. I spoke to my dad about it who seemed to be very nonchalant about it. -.-

So I've had a steady light for a month-month and a half when I was dropping someone off and while I was stopped at a stop sign, my car started to vibrate/shake and the CEL began blinking. When I turned it on a while later, the light was steady.

I went to an Advanced AutoZone and had codes: P0300, P0421, and P0090 read. -.- I've been looking long and hard for solutions online and my father's mechanic friend will be looking at it when he gets the chance.

This car is the only car my family owns and I'm the only one who drives so you can see my concern. When I started the car on a cold start this morning, it was vibrating and the CEL was blinking when I was letting it warm up. There was also the faint smell of gas. SIGH. What to do? My family member is due at the doctor this Thursday which is a half hour away (and the only reason I really ever wanted a car was to help out).

So if you could provide some guidance, that would be goooood.

Thanks.

P.S. We just changed the oil about 2 months ago.And the mileage is around 100,400K

 

Kas: look at the unofficial user's guide to the '95-'98 Mazda Protege. I know yours is newer but most of that still applies.

 

p0090 is fuel pressure control, p0300 is random misfire and p0421 ic catalytic converter efficiency. p0090 could develop on misfires, giving you other codes. gas smell too? the first check i would do, and the easiest one is to disconnect the vacuum line that goes to the fuel pressure regulator. if you see fuel in the tube of the regulator and/or in the vacuum line, it means the regulator diaphragm broke and fuel is leaking out the regulator, into the vacuum line (in that condition, the regulator wont work). if that is the case, replace the regulator. if it is ok, start the engine and check that you can feel vacuum in that line. if you dont feel any vacuum with your finger, you can try disconnecting and connecting the electrical plug that goes to the solenoid that has the other end of the fuel pressure regulator vacuum line. ( i think the name is PRC Valve). that could reset a dirty electrical connection. start there and let us know.

 

let the record show that i cant find a P0090 code in the books. my opinion is based on a P0090 search on google.

 

Blinking cel is definitely misfires.
The fuel that powers your vehicle is meant to burn IN THE COMBUSTION CHAMBER ONLY. Any fuel that leaves the combustion chamber unburned will enter the exhaust system and “light off” when it reaches the converter. This can “superheat” the converter to temperatures far above normal operating conditions and cause a CONVERTER MELTDOWN.
The excess unburned fuel ignited when it struck the hot ceramic catalyst and drove the temperature far above the normal operating condition of the converter. The ceramic catalyst is unable to withstand the extremely high temperature and begins to melt. The ceramic collapses and the converter is destroyed. The melted ceramic may block the exhaust flow and cause additional damage to the engine. A converter glowing red-hot or evidence of heat discoloration confirms this situation.
The misfires can lead to cat blockage as a result of above causing your P0421 code!