P300 code

[tyreebut]

I have taken my car into the Mazda dealer three times and the problem hasn't been fixed. The first time they drove it and just cleared the code. The second time they told me the spark plugs needed to be replaced. The dealer told me it would be $400.00 so i bought autolite Iridiums XP's but the egine light cleared and then came back on. It has come off and on lately. So I took it to the dealer a third time and I told them to thoroughly check the coil packs, etc. They told me again it was the spark plugs. So in California it is $90 each time I take it to the dealer. I just replaced the spark plugs with NGK's. The light cleared yesterday but came back on this morning when I started the car to go to work. When I get home I am going to disconnect the battery to see if I can reset the engine light. Can someone provide me with any information what the problem might be otherwise I will end up paying the dealer $400 to correct the problem.

[Vansquish]

I think the code is a P0300, right? That's a random misfire. You might want to swap the coil packs from cylinder-to-cylinder and see if you can narrow down whether you've got a single bad coil-pack (that is, if the misfire starts to manifest in a single cylinder).

What spark plug gap are you running? It should be between 0.024" and 0.027" per Mazda's revised service manual from 2010.

What modifications do you have on the car?

[tyreebut]

My car is bone stock. The plugs are gaped at .027. Does it matter which coil pack that I use on each spark plug? I marked them before I changed the spark plug to ensure I put the correct coil pack on the correct plug.

[Vansquish]

The wires leading to each plug cylinder must remain in the same orientation they came in. However, you can unplug and move the individual coil packs from cylinder to cylinder.

Mark each one, and move them around.

[Code Monkey]

It's a random misfire on all 4 cylinders so I doubt that moving the coilpacks around will help but try and see. What are exactly the spark plugs you bought (model/part number)?

[tyreebut]

NGK Laser Iridium part #95369 from Oreilly's

[Code Monkey]

Originally Posted by tyreebut NGK Laser Iridium part #95369 from Oreilly's

This points to a

SILTR6A7G

SILTR6A7G
SILTR6A7G

[Say Chi Sin Lo]

Your P030X (X = cylinder #) keeps coming back? Please keep us updated.

I had a P030X code before, cleared it and never came back. I would like to know how yours turn out, thanks!

[tyreebut]

I made an error I put the stock # down not the part # of SILTR6A7G. I cleared the code by disconnecting the battery and I am monitoring my car to see if the check engine light comes back on.

[MD1032]

Originally Posted by Code Monkey This points to a SILTR6A7G plug, you need an NGK ILTR6A-8G (3787), which is a stock heat range plug.

I disagree. SILTR6A7G are the factory plugs for the Gen2. Here is the picture of the factory plugs I pulled out of my car not long ago. They are made by NGK and have the part number printed on them. The number "6" refers to the heat range, not the second to last digit.



Also, if you go here, and type in my car (2012 Mazdaspeed3), it will direct you to the SILTR6A7G.

PartCat

As far as I know, the only difference between the ILTR6A-8G, which are stock for the Gen1 and MS6, and the SILTR6A-7G is that the gap was decreased from 0.032" to 0.028". They are both NGK laser iridium plugs. I agree with OP's decision to buy the smaller gapped plug as it is less prone to spark blowout.

[tyreebut]

Well at this point I am getting frustrated. I put the NGK plugs in, disconnected the battery to remove the check engine light. The check engine light came back on after 4 days. I am going to check the plugs and switch the coil packs around to see if one of the coil packs need replaced. If anyone has any ideas how to resolve please let me know. I really don't want to have to take it back to the dealer.

[MD1032]

Did you already check to make sure all of the ground connections to the chassis are good?

I have uploaded the directive for troubleshooting this code from the service manual. Normally I wouldn't post this because you're a brownie and really you should just buy VIP so you can download a copy of the service manual. Merry Christmas.

Personally I would start with the basics. Log in closed loop and monitor fuel pressure, AFR, MAF voltage, intake air temp, throttle position, oxygen sensor voltage for both sensors, short term fuel trim, and long term fuel trim, grouping as needed so that torque or whatever app you're using can log with enough resolution to to see any electrical spikes or odd things. I had a misfire a couple weeks ago on my car due to a dirty fuel injector (using fuel injector cleaner in-tank resolved the problem) and it was really noticeable when the car was cold. Note any behavior like this and monitor applicable parameters closely under these conditions.

Also, please post the tune you are using so we can examine your MAF curve. It always amazes me how important a good MAF curve is on this car. If you don't have a good one, it will cause all kinds of problems.

[tyreebut]

Thank you very much. At this point I will become a VIP with the issues I have been having with this car. It's funny that you mention the fuel injector cleaner. When I did use it my check engine light cleared and that is with the Autolite plugs not the NGK's.

[JSmith]

Mileage on the car? In which cylinders is the dealer seeing the misfires?

[highwayrun]

I had a P0300 code for a long time and finally solved it. The cause was a stuck-open EGR valve.

Oddly enough, the car didn't throw an EGR-specific code, but the vacuum at idle dropped from 20 in.Hg to 18 in.Hg overnight, and kept dropping as the weeks went by, bottoming at around 9 in.Hg. If you can measure vacuum, e.g. using the Torque app, that would give some insight. Also, if you can't even build any pressure during a boost leak test, that might be a clue the EGR valve is stuck open.

To fix, I removed the actuator on top the EGR valve and worked the pintle on the valve a few times until it moved freely. It might not be a permanent fix, but it confirmed the issue in my case.

Maybe this helps. Good luck.

[tyreebut]

Originally Posted by JSmith Mileage on the car? In which cylinders is the dealer seeing the misfires?

When I had the serviced on July 28, 2015 the invoice just states it was a P0300 code they inspected the TSBS and SM's. Found TSB 01-015/14 and they cleared it. I took it back the August 17, 2015 they inspected and found P0300 code and said plugs were carboned up. I replaced them with autolites. I took it back in December 18, 2015 and P0300 code and they said it was the spark plugs. I put in NGK's this time. I had it scanned yesterday and the P0300 code and P2006 code showed. I got it back home and took off all the coil packs and stretched the springs. I also checked all connnections. The check engine light is still on. The vehicle currently has 62,800 k on it.

[JSmith]

It matters which cylinders. See the TSB here. Code P0300 TSB 01-015-014