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post #1 of 32 (permalink) Old 03-31-2017, 07:26 PM Thread Starter
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Misfires, System Too Lean/Rich

Have a 2004 Mazda 6 Sport GT 3.0L 237,000kms

Stored Codes:
P0300 - random Misfire
P0171 - System too lean bank 1
P0175 - Fuel System too Rich bank 2

Pending Codes:
P0300 - random Misfire
P0171 - System too lean bank 1
P0175 - Fuel System too Rich bank 2
P0301 - Cylinder 1 misfire
P0306 - Cylinder 6 misfire

Not really running too rough, a little rough at idle and only sometime does it seem to bog down under load, valve cover had a very bad leak initially, no noticeable vacuum leaks (I can't hear any)

Things that have been done to try and resolve problem (in order):
1) Switched coils plug around in Cylinder 4-6 to try and see if it would change, still stayed on 6
2) new fuel injector for 6 (since running rich on that side, and misfiring at 6)
3) new intake manifold gaskets and PCV when the injector was done
4)cleaned MAF, worked for about 10 kms, them codes came back
5)got a new MAF sensor, put it on, car ran BAD! couldnt get up to speed, misfiring horribly. Put the old one back one, back to what it was before
6) took to mazda dealer for diagnostic, they said the front pre-cat was clogged. changed that and performance got better, but still all the codes
7) changed valve cover gasket, and 3 new plugs on front (old plugs looked newer, but had oil on them)

Here I am !

Freeze frame data from today:

DTC for which Freeze Frame was Stored P0300
Fuel System 1 Status Open Loop - due to driving conditions
Fuel System 2 Status Open Loop - due to driving conditions
Calculated LOAD Value 49.80 %
Engine Coolant Temp 91.40 F
Short Term Fuel Trim - Bank 1 0.00 %
Long Term Fuel Trim - Bank 1 15.63 %
Short Term Fuel Trim - Bank 2 0.00 %
Long Term Fuel Trim - Bank 2 -23.44 %
Engine RPM 4,139.00 rpm
Vehicle Speed Sensor 59.03 mph
Ignition Timing Advance #1 Cylinder 25.50
Intake Air Temperature 33.80 F
Air Flow Rate Mass Air Flow Sensor 6.40 lb/min
Absolute Throttle Position 27.06 %
Time Since Engine Start 104 sec
Commanded EGR 0.00 %
Commanded Evaporative Purge 0.00 %
Fuel Level Input 82.35 %
# Warm-ups since DTC Cleared 0
Distance since DTC Cleared 0.00 mi
Barometric Pressure 29.31 inHg
Catalyst Temperature Bank 1 - Sensor 1 1,042.34 F
Catalyst Temperature Bank 2 - Sensor 1 1,042.34 F
Control Module Voltage 14.62 V
Absolute Load Value 41.57 %
Relative Throttle Position 22.35 %
Absolute Throttle Position B 41.96 %
Accelerator Pedal Position D 41.57 %
Accelerator Pedal Position E 30.20 %
Commanded Throttle Actuator 22.35 %

Next step this weekend, got a can of carb cleaner, going to spray to see if I can find a vacuum leak.
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post #2 of 32 (permalink) Old 03-31-2017, 09:26 PM
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Do you have O2 readings?
I recently came across something like this with big disparities in rich-to-lean banks. Mine was due to a clogged catalyst.
Idle was smooth and really could tell nothing was wrong. Bogged under load (early symptom) then as it advanced it got worse.

2004 Wagon S 3.0, 5-speed ATX, Performance White (A2N) 167,000mi
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post #3 of 32 (permalink) Old 04-01-2017, 08:34 AM Thread Starter
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`
That was all that I was able to get from my OBD2 Reader. When I replaced the front pre catalytic converter, the old was was very clogged, o2 sensors did have carbon on them so i did spray them down with carb cleaner (it didnt get it all off). The new cat was put on less than a week ago, and these are the readings after the new cat. I did not attempt to check the rear one as it is a pain to get to, and this is the first time the Cylinder 1 came up. Its usually the 6, and sometime the 4 or 5 pops up but then goes away. The lean code also went away on it own last week then came back. The random misfire is the only one that is constantly there from as soon as a code is erased and the car is turned back on.
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post #4 of 32 (permalink) Old 04-03-2017, 06:13 PM Thread Starter
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UPDATE:

Sprayed all of the vacuum lines down with carb cleaner, nothing.

Took off the MAF again and cleaned it again with electrical cleaner, realized the o-ring was stretched and not fitting in so I did a jimmy rig on it and used gasket sealer instead to seal it (will get a new one once I know whether or not the MAF is good). Let it dry for about 18 hrs to be safe. Also checked throttle body, clean as a whistle from what I could see.

Drove it today, about 50kms in total, the CEL came on right away from turning the car on this morning. I checked it when I got home, and now the only codes that are there are the P0306 - Cylinder 6 Misfire (stored and pending) and P0175 - System to rich bank 2.

Now, the random misfire ALWAYS comes back right away, so I'm not sure if I am out of the clear or not for the random misfire. I am going to switch coils from 6 to 4 and see if the misfire moves and will update again tomorrow. ANY thoughts would be greatly appreciated.

Freeze frame data from today:

DTC for which Freeze Frame was Stored P0306
Fuel System 1 Status Open Loop
Fuel System 2 Status Open Loop
Calculated LOAD Value 36.86 %
Engine Coolant Temp 35.60 F
Short Term Fuel Trim - Bank 1 0.00 %
Long Term Fuel Trim - Bank 1 20.31 %
Short Term Fuel Trim - Bank 2 0.00 %
Long Term Fuel Trim - Bank 2 -25.00 %
Engine RPM 1,499.00 rpm
Vehicle Speed Sensor 0.00 mph
Ignition Timing Advance #1 Cylinder 16.50
Intake Air Temperature 39.20 F
Air Flow Rate Mass Air Flow Sensor 1.59 lb/min
Absolute Throttle Position 17.65 %
Time Since Engine Start 10 sec
Commanded EGR 0.00 %
Commanded Evaporative Purge 0.00 %
Fuel Level Input 21.18 %
# Warm-ups since DTC Cleared 0
Distance since DTC Cleared 0.00 mi
Barometric Pressure 29.31 inHg
Catalyst Temperature Bank 1 - Sensor 1 50.54 F
Catalyst Temperature Bank 2 - Sensor 1 50.54 F
Control Module Voltage 14.41 V
Absolute Load Value 28.24 %
Relative Throttle Position 8.24 %
Absolute Throttle Position B 22.75 %
Accelerator Pedal Position D 31.76 %
Accelerator Pedal Position E 20.78 %
Commanded Throttle Actuator 7.84 %
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post #5 of 32 (permalink) Old 04-03-2017, 06:31 PM
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If your front catalysts were clogged the downstream ones are not far behind.
When this job gets done it should be done with all four. My 2 cents
Still could be clogged cats.
Here is what my workshop manual says for the P0175
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2004 Wagon S 3.0, 5-speed ATX, Performance White (A2N) 167,000mi
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post #6 of 32 (permalink) Old 04-03-2017, 06:49 PM Thread Starter
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I have a feeling I might have to do that. I'm just frustrated because I bought the car certified and etested and about a month after buying it I found tape over the CEL. I might get it up on the ramps as well and test the temperature to see if I can determine whether the cats are bad based on that without having to take everything apart.

Thank you for the information from the manual, I am going to print that off and go through it on the weekend to see what I can come up with from there.
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post #7 of 32 (permalink) Old 04-03-2017, 07:45 PM
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Quote:
Originally Posted by Megan Boswarva View Post
I have a feeling I might have to do that. I'm just frustrated because I bought the car certified and etested and about a month after buying it I found tape over the CEL. I might get it up on the ramps as well and test the temperature to see if I can determine whether the cats are bad based on that without having to take everything apart.

Thank you for the information from the manual, I am going to print that off and go through it on the weekend to see what I can come up with from there.
Arrrgh, how frustrating. I really feel for you. I just walked this same road.

If your OBD2 reader can give live data and you selected all 4 O2 sensors that would clear up pretty quick I think what is happening.
Sensor 1 should oscillate between 0.1 and 0.8 volts like a Sin wave. Every time the voltage goes up that means there is unburnt fuel in the exhaust (reacting with the sensor and closing the circuit) Too much fuel is bad so the computer reduced the fuel and thus the voltage goes down.
The downstream sensors should be very stable and low voltage 0.1ish (provided the catalyst is working.) This sensor sees how the converter is responding to the input exhaust and tells the computer if it is still working (the catalyst that is)

Here is a printout from my system with a bad catalyst
See how O2S11 and O2S21 are moving up and down with a range near 1v (0.78v)
The other sensor O2S12 is oscillating a little behind the upstream sensors but only up to 0.1v and O2S22 is not really moving at all. This is the clogged catalyst.
O2 S22 means bank 2 sensor 2 (downstream)

The IR temp may help (mine didn't really show). You could also pull the upstream sensors out and see if your power improves. It will be a little loud but you should know within the first drive. Mine got so bad I could not accelerate beyond about 45mph at the end

Good Luck
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post #8 of 32 (permalink) Old 04-04-2017, 09:44 AM Thread Starter
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Update:

Switched coils last night, drove this morning and checked the codes again, still cylinder 6 misfire, and system too lean bank 1. Throwing me off since everything linked to cylinder 6 has been changed (fuel injector, spark plug, coil). The random misfire has yet to reappear (I presume the sealing of the MAF was the fix for that..). I understand the possibility of a clogged catalyst, but wouldnt that effect more than one cylinder?
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post #9 of 32 (permalink) Old 04-04-2017, 10:37 AM
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What about the harness for cylinder 6?

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post #10 of 32 (permalink) Old 04-04-2017, 11:53 AM Thread Starter
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It looks ok from what I have looked at. The harness for both 4 and 5 have been cut and repaired by previous owner. I will inspect further up the wires and see if it is damaged in another area.
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