I was cruising down a frontage road and while coming to a stop the vehicle started running really rough. I hit the brakes kinda hard when coming to a stop and thats when the motor seemed be misfiring. The check engine light came on in a flashing mode then the light was continuous there after. I put the vehicle in neutral and then in park the rough idle continued. After about 40 seconds at a stop light, the light turned green and when I hit the throttle the vehicle would barely move....the engine seemed to be bogging or not getting enough fuel etc...No back fires occured and then seconds later the car accelerated like normal, but the check engine light stayed on. Even though the misfiring seemed to stop while cruising I would let off the throttle and coast...the engine would ever so lightly surge a little while coasting, not sure why. Got the car home, ran a diagnotic and it spit out the infomous P300 code(random misfire). I know there are a lot things that can cause a misfire, anyone know what the usual culprit is? I checked all the spark plugs and they are buring normal, all spark plug wire boots are in perfect shape(new), and there is no evidence of corrosion on the connectors of the ignition coils. I cleared the code and now the car is running normal again. I know its a matter of time before this happens again. Any ideas???
2002 protege dx 2.0ltr stalling
- Thread starter YenkoZL1
- Start date
cuzitskyle
Member
Check you air intake hose. I had this same issue and figured it was a fire issue, turned out it was the air. The rubber air intake hose had a large hole in it after the MAF sensor, on the bottom part of the hose in the "flexible" area. To verify that this was the issue, I wrapped the hose in duct tape and reset the ECU. The duct tape temporarily fixed the problem while I ordered a new hose for $25~30. Replaced the hose and reset the ECU, haven't had the issue since (6 months or more).
It seems to be the intake hose. The bottom part of the hose around the ribbed area is dry rotted and cracked. I wrapped mine in electrical tape for now unitl the new hose comes in. Hopefully this solves the issue, if not, then I'm thinking maybe the MAF. I know they can go bad at random and cause a lot issues or symptoms that make you think it's something other than the MAF. I appreciate the heads up info "cuzitskyle."
Ok, so the misfire occured again. Causing the vehicle to go into limp mode for a few seconds. Same p300 code. So this time I ireplaced the EGR valve with a BWD and the upper fuel sending unit(genuine mazda) with the built in high pressure filter and fuel pump(denso) and strainer. After completing the install the car struggles starting, and will idle but not accelerate withou bogging out. I feel the fuel pump from Denso is a dud. So I took out the new pump and reinstalled the factory pump and the car still struggled to start but ran better with the factory pump than it did with the denso pump. How can this happen? Everything is install correctly. I dont think its the EGR vavle only b/c its only effective when the vehicle is in motion, and the symptons take place while in park when reving the engine...any ideas? I'm gonna get a new fuel regulator and buy a mazda geniune pump just in case it's a coincidence the old pump is bad and the new one happened to be faulty. Surprised cause Denso makes good stuff. Maybe the fuel reguator was causing the p300 code the whole time....kinda running out of ideas. All electrical components checked out ok, so I figured the EGR vavle and fuel could be the issue since they've never been serviced. Any past experiences are welcome! 
Installed the new Genuine Mazda Fuel Pressure Regulator and the new Geniune Mazda Fuel Pump. This seemed to help but the car is still not running right. The car takes way too long to start warm or cold. And once the engine ignites it's a rough start. Car seems to idle fine but when I give it gas the motors starts to bog down for a few seconds and then the rpm's will start to pick up. Something's still not right. My only other ideas are potentially the CKP or the CMP. Not too sure what these two senors control in relation to fuel and spark. Any help would be great. My last thought would be the Fuel pump relay. I've heard that if these are faulty they can cause hard starts and cause the vehicle to run rough under acceleration.
After replacing the Fuel Pump Relay for good measure the symptoms didnt go away. So I gave in and let my local Mazda Dealer have a look at it. Turns out the fuel pressure was waaay low. Only 16psi versus factory spec of 40psi. It's a good thing that the fuel pump and the whole fuel pump unit it sits in came from that dealer a genuine Mazda part. They are going to warranty the parts and then I pay the labor. No idea as to how this can happen. I asked them if I installed the parts incorrectly or if I damaged something during the install. They said no, and they don't know why its failing. They are going to order the entire fuel unit as one from the factory vs the way I order them which was in individual pieces. Basically the pump will come installed in the housing. I am baffled. And I guess so are they. Hope this works. haha The pump and unit are only a week old!
Hope this works. haha The pump and unit are only a week old!Dealer installed the pump and everything is up and running like normal. I am very pleased.....Plus the dealer gave me 20% off the labor so all in all $230 in labor total. I am still baffled as to how this can happen with 2 pumps once!? But it is what it is I guess.
