I am having some issues with my 2002 Mazda Protege 5 and I am looking for advice. My issues started when I brought my Mazda in for its 30,000 Mile Transmission Flush. My car was 3 years, just at the 30,000 mile mark when I brought it in for maintenance @ my Mazda dealership. Upon picking up my car, I started it, and it made a strange sound and was loud, and my check engine light came on. I drove it right back in the dealer doors....but unfortunatly I think they just reset the check engine light and did not look further at that time. That was 7000 miles ago. Since then, I had issues where my car would not start and my engine light was on. Something was replaced, I cannot remember what it was. ( It was a warrantied part, though) My car was fine for a few months. Then, I started having issues where I would drive my car for 15 minutes on the highway, and all of a sudden my acceleration would go down. My engine light would flash and then stay on. In the meantime, to accelerate, I would have to downshift, then it would begin to accelerate again, and then be on my way. I brought it back in, and they replaced the EGR valve. Ok, great. It worked for a few weeks, and now I am having the same issues. I have it back at my mazda dealer, but for 5 days now, every time they say that they have it fixed, I drive it, and it happens to me. They put 70 miles on it last time, and I drove it 1 mile off the lot, and my light is on, and I cant accelerate. They say the codes are different each time. The last 2 codes were Random Engine Misfires. I have tried everything, and asked them to look at the Midflow Air Sensor, the Oxygen Sensors, relook at everything done from the 30,000 mile flush...etc. Does anyone here have any advice? It would be greatly appreciated!

 

Was anything else done at the service besides a transmission flush? You stated that when you first started it after the service it made a strange sound and then was loud and CEL came on. CEL was reset apparantly but is it still loud? Sounded like maybe an exhaust pipe was left loose was why I wondered. The most common cause of an intermittent random missfire (the code P0300) is the EGR valve sticking open due to rust accumulation on the pintel shaft. The valve is normally opened when driving steady speeds but when you come to an idle or closed throttle condition the valve should close completely. If it does not then the engine will run rough and CEL will flash. (CEL flashing by the way means only one thing, a severe missfire is being detected that could damage the catalytic converters ). This is probably why they replaced the EGR valve although given your description of the power loss occuring on accel and then CEL flashes it probably was not the valve.
Does the power loss occur first and then CEL flash and then stay on? If so have them check the fuel pump pressure while it is being driven. Loss of fuel pressure sounds more like what you have occuring. As pump pressure drops you feel the power loss untill pressure gets so low that injector spray amount is insufficient and engine starts missing. Have seen this on more then one later model Protege.
The ignition coils have also had some problems but you would not feel a smooth power loss if a coil quit firing.
Question there as well. When this power loss occurs is the engine still smooth like you were just letting off the gas or does it feel rough and jerky like the engine is missfiring?