in need of help for one and only car in use

[kasruesao]

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. I also smelled a faint fuel odor 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. The car is at around 100,500K miles and we changed the oil...at 100300Kish.

[FE3-323]

What spark plugs were used?? brand? part number?
if anything besides NGK's were put in they need to be replaced again- get the standard V-power ones. no need for platinum or iridium.

P0421 is a bad secondary O2 sensor- (do you have a header?) if not then buy another O2 sensor.

Did you recently fill up with gas? what octane do you use?

[progt91]

Egr sticking will give you a p0300 code. Pull out the egr and clean it all up. Make sure the valve opens and closes good. Do that ASAP or you will burn out the manifold converter.