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13 Mazda 3 skyactiv p0303 and sometimes p0300

  • Ziptieracing
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07 Jan 2018 21:48 - 07 Jan 2018 22:18 #16554 by Ziptieracing
13 Mazda 3 skyactiv p0303 and sometimes p0300 was created by Ziptieracing
Hi everyone,

I'm working on a 2013 mazda 3 with the 2.0 skyactiv motor, 6 speed auto, and roughly 75k miles. To my knowledge it's never been in an accident and no work has been done to it prior to the misfire besides the usual maintenance (bleed brakes, change oil, change coolant, change transmission fluid to fix some hesitation and rough shifting)

When the weather is cold and the engine is under high load, it will misfire to the point the car puts itself into a safe mode where it shuts off the injector to cylinder 3 and limits throttle to about 20% to prevent catalyst damage (according to the factory service manual) apparently it does it whenever the engine misfires more than once every 200 revolutions. However the misfire counter on cylinder 3 will be chugging along the entire time, with an occasional misfire on cylinder 1 or 4 (occurring once every 250-500 cylinder 3 misfires). Sometimes the engine runs rougher than other times, but it generally isn't extremely noticeable. Generally the cold makes it worse.

What I have checked:

-The spark plugs are scheduled to be replaced at 75k miles. I changed them at 69k. No improvement.
-I borrowed a known good low mileage coil pack from a friend and swapped it around each cylinder. Still got misfires.
-Sprayed the entire intake tract and all hoses with TB cleaner looking for a vac leak.
-Walnut blasted the intake valves (they were extra crusty)
-Replaced the PCV valve, but did not check the air oil separator
-Flashed the PCM and TCM to the latest software/calibration from mazda

Using Mazda IDS (mazda's official diagnostic software) I checked the following sensors according to the mazda service manual and all were within spec:
-Alternator duty
-rail fuel pressure (this is a DI motor)
-high pressure fuel pump duty cycle
-fuel tank pressure
-Ambient air temp
-barometric pressure sensor (located in the ECU)
-Accelerator position sensor 1
-Accelerator position sensor 2
-Engine coolant temp sensors 1 and 2
-Intake air temp sensors 1 and 2 (on MAP and MAF)
-MAF
-MAP
-Vehicle speed sensor
-A/F sensor current
-02 sensor voltage
-injection pulse width
-throttle body resistance according to manual + visual check of operation

The only anomalies I could find were:
-relative throttle position: (idle, accelerator pedal depressed) FSM spec=12%, 82% Actual measured= 3%, 60%
-long term fuel trim (idle, 2000 rpm, 4000 rpm) FSM spec: -2.34%, -0.78%, -0.78 Actual measured= +0.78, +7.03,+9.37
-Heated 02 sensor fuel trim at idle FSM spec= 0.5% Actual measured= 1.57
-Short term fuel trim (idle, 2000 rpm, 4000 rpm)FSM spec: 1.56%, -3.12%, -8.59% Actual measured= +2-3%,-2%,-3%
-Exhaust VVT oil control valve duty cycle (idle, 2000 rpm) FSM spec: 0%, 46% Actual measured=0%,52-62%
-Fuel Pulse width duration spiked off the chart (high) a few times for a fraction of a second
-The hydraulic serpentine belt tensioner releases a small spark to the engine block occasionally (1-3 times a minute) but it does not correspond to the misfire counter.


What I did not check:
Glove test of the oil fill port to check for crankcase pressure.
Physical inspection of VVT motor and actuator (no tools with me, plus single digit temps)
Crank sensor
Cam sensors (vvt on both cams)
Injector resistance
Low pressure fuel pump
EVAP purge solenoid
Proper intake pressure check for leaks

I'll likely do a check of the above items this upcoming weekend. But based on the above, anyone have a clue what else I should be looking at or if I can make a determination with the above data? I am leaning towards a throttle body given the relative throttle position deviation, however since I checked resistance and both the throttle position sensors are working to spec, I don't feel confident. Also with the tensioner spark makes me feel suspicious. It doesn't look like anything more than static electricity, and there are no wires around that area, but it can't be good for sensor grounds.

Thanks everyone
Last edit: 07 Jan 2018 22:18 by Ziptieracing. Reason: More details

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05 Mar 2019 17:21 #27618 by Ziptieracing
Replied by Ziptieracing on topic 13 Mazda 3 skyactiv p0303 and sometimes p0300
I hate to be the guy that doesn’t provide the solution to his own inquiry, but I was that guy.

So everything seemed fine because it was.

The issue was a clogged cylinder 3 injector. I haven’t had a chance to send it out for cleaning, to see if it is dead but the resistance on it was within spec. Apparently this is relatively common with higher mileage Mazda skyactiv motors. Mazda claims its from cheap gas according to a TSB, I vaguely recall reading. But your mileage may vary.

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