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Ted the Technician
Ted the Technician, ASE Certified Technician
Category: Car
Satisfied Customers: 122
Experience:  ASE Certified Technician, Former GM Master Technician, Former Lexus Master Diagnostic Specialist
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98 mazda millenia: i have p300 random misfire..injectors..p0301

Customer Question

Please I need a mazda expert
why do i have p0300 random misfire on my 98 mazda millinia 2.5 after i changed one of my injectors because I had a p0301. Please let me what you think. And I don't if I left something unplug or what but I checked everything.
Submitted: 8 years ago.
Category: Car
Expert:  Ted the Technician replied 8 years ago.

Hi, I,m Ted and I will assist you.


I will assume that replacing the injector fixed the original problem. What may have happened is when you removed the fuel rail to replace the injector, when you went to reassemble it you may have not gotten the injectors to seal in the intake. a vacuum leak from here can cause a p0300 because it can affect more than one cylinder. Did you clean the intake holes and lubricate the injector orings when you reassembled the parts.

Customer: replied 8 years ago.
Yes I lubricated the oring but I didn't clean the intake hole and I only took out one injector didn't touch the rest. If i clear the code the it won't come back on unless I'm at idle for a while or at the stop light for a while. Let me know
Expert:  Ted the Technician replied 8 years ago.
I would lean towards a vacuum leak. If you have a propane torch you can turn it on but not light it and go around the intake and vacuum lines. If the idle changes you may have found your leak.
Customer: replied 8 years ago.
Can I also use carburator cleaner and spray it all around.
Expert:  Ted the Technician replied 8 years ago.
You can just be careful it can ignite. Keep it away from anything hot or sparking.