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P0300/P0401, rough idle and CEL

Mazda CX-7 This sporty turbocharged 4 cylinder SUV combines the spirit of a performance car with the versatility of an SUV.

P0300/P0401, rough idle and CEL

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  #1  
Old 10-10-2018, 07:38 AM
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Location: Kentucky
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Default P0300/P0401, rough idle and CEL

I'm sure I'm resurrecting a common thread here but would like any advice regarding a CEL with a P0300 and P0401 code. I have replaced the spark plugs and ignition coils with no change. I unplugged the EGR valve to see if that would make a difference before I take it off to try cleaning it. Still have a rough idle going. Runs OK once it's going but idles rough and seems to possibly experience a bit of a power loss. If you have an answer as to what this could be other than these components I mentioned, a description or picture of the problem child part in question would be helpful. I'm fairly new to the Mazda experience. 2008 CX-7 is the car. Thank you...
 
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Old 10-10-2018, 10:02 AM
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Location: Pittsburgh, Pa
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P0300 MAZDA - Random Cylinder Misfire Detected
Possible causes Faulty spark plug (s) Faulty ignition coil (s
) Clogged or faulty fuel injector (s)
Intake air leak Fuel injectors harness is open or shorted
Fuel Injectors circuit poor electrical connection
Ignition coils harness is open or shorted
Ignition coils circuit poor electrical connection
Insufficient cylinders compression
Incorrect fuel pressure


P0401 MAZDA - Exhaust Gas Recirculation Flow Insufficient Detected
Possible causes EGR passage clogged
Faulty EGR Vacuum Modulator Valve
Faulty EGR Valve
Faulty EGR solenoid valve
EGR solenoid valve harness is open or shorted
EGR solenoid valve circuit poor electrical connection
Dead (Weak) battery
Faulty EGR temperature sensor and circuit Exhaust gas leaks
 
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Old 10-10-2018, 10:13 AM
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Thank you for the list. Looks like Iím at least looking down the right rabbit hole. Iíll take the EGR valve off and clean it and try that. A new one looks like it rims over $200. I also put Sea Foam into the gas to clean the injectors. Hopefully that helps. The spark plugs and ignition coils are brand new so I can rule those out. If anyone else has any ideas Iím all ears.
 
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