P0300 is a generic misfire code, it doesn't specify a cylinder (eg. P0301 cylinder #1, P0304 cylinder #4). Therefore its not likely realted to one cylinder like a plug, coil or one fuel injector, likely something related to all cylinders, possibly a bad 02 sensor reading (most likely), a fuel pressure regulator, low fuel pressure or partially plugged fuel filter. Change the fuel filter cheapest and easiest, then look into 02 sensor.
I forgot to mention I changed the fuel filer first thing. guess i will go with 02 sensor and then work on fuel system. Thank you for the advise!
P0300 - Random/Multiple Cylinder Misfire Detected
When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the crankshaft position (CKP) sensor (POS) signal to vary, Powertrain Control Module (PCM) or Electronic Control Module (ECM) can determine that a misfire is occurring.
Causes:
- Improper spark plug
- Insufficient compression
- Incorrect fuel pressure
- The injector circuit is open or shorted
- Fuel injectors may be faulty
- Intake air leak
- The ignition signal circuit is open or shorted
Solutions:
- Perform Injector Service
- Replace Spark Plugs
- Replace Injectors
- Replace Ignition Coils
Thank you for the help! Just wanted to let you know I had the fuel system and injectors checked as you suggested and it wasn't the issue either. So on the advise of a friend I replaced the computer and after having it programmed by the dealer, my car runs better than it ever has since I have owned it! and it cleared all the codes!
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The only thing left would be fuel. Check fuel pressure , replace the fuel filter, and check the injectors(ohm's from 11 to 15) and the injector harness. Mostly on the harness make sure you didnt pinch a wire putting it back together, especially the map and coolant wires.
Testimonial: "Thank you for the help! Just wanted to let you know I had the fuel system and injectors checked as you suggested and it wasn't the issue either. So on the advise of a friend I replaced the computer and after having it programmed by the dealer, my car runs better than it ever has since I have owned it! and it cleared all the codes!"
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Inspect the EIS towers and plug the wire connections for corrosion or other signs of poor retention at connections.
The electronic ignition (EI) module supplies a signal to the PCM whenever it determines that the #4 cylinder fired on its compression stroke. Because of opposite coil tower polarity, the simultaneous fir of #1 and #4 cylinders are of opposite polarity as well. Under most conditions, except decel, the waste spark cylinder fires before the compression cylinder in sequence. The EI module can determine this polarity sequence and voltage amplitude by using capacitive pickup plates located under the 1/4 coil. If the module senses a positive to negative sequence and high negative spike when #4 is on TDC, it pulls the PCM cam signal to ground signaling that #4 has just fired on compression. This signal along with the double pulse received from the CKP sensor, synchronizes spark and fuel timing.
Beside plugs , plug wires need to be replaced as well !
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