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Thread: Help - Got a CEL P0300 Tonight

  1. #1
    Join Date
    Aug 2010
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    Unhappy Help - Got a CEL P0300 Tonight

    HI all,

    While driving home this evening when the Check Engine Light started to flash then stayed on. Scared the crap out of me as I've never had this before.

    I was reluctant to pull over and and restart the car just in case it wouldn't start again so I drove home very carefully. (The thought of being stuck on a freeway with wife and 2kids had crossed my mind)

    Scan tool shows it as a P0300 - Random/Multiple Cyclinder Misfire Detected and from a previous thread listing the OBD codes - P0300 Random misfire detected Flash/ON 2 Misfire.

    I cleared the code and then took the car around the block. It hasn't come back again this evening.

    Nothing has changed since the Hypertech tune went in last month and the only other mod is the MZR SRI prior to the Hypertech.

    Can anyone shed any light on this and point me in the direction of where to start troubleshooting ... please ?
    Trying to keep it subtle ... | COBB AccessPort | COBB DP | CP-e HPFP | CorkSport TMIC | TurboSmart BPV | Denso ITV22| CorkSport Boost Tubes | SURE Full3 Aeros | SURE REM (Street) | SURE AGS SS Shift Knob | 2XS SSP + SURE CounterShift | Speedline Front Strut Brace | Whiteline RSB | Prima Paint Protection

  2. #2
    Join Date
    Nov 2008
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    Fuel, spark, coils, leads etc?

    Never heard of anyone getting that one before...

  3. #3
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    Fuel...same place I always fill up...Shell Optimax.
    I'll check the leads to make sure nothing has come off.

    Will take it for a drive today and see how it goes. I'm hoping it doesn't return and was just a once off.

  4. #4
    Join Date
    Nov 2008
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    Return it back to stock tune and take it to mazda for a check.

  5. #5

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    Hey mate. Did the code ever return?my CEL came on this morning after 15min of driving. Rang nrma to get code read.

    Nothing showed up after two scans then it p0300 came up and his Bluetooth reader lost connection. He rescanned two more times but nothing came on.

    Gotta wait until after work to hook up dashdaq.

    The only thing that comes to light is I filled up with vpower last week. Usually fill up with ultimate.

    New plugs were replaced last month by TH.

    Sent from my HTC Desire HD using Tapatalk

  6. #6

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    I would put odds on the plug gaps being too wide.

    Missfire is a common name for spark blow out.

    Usually this is a problem in high boost applications, but its possible I suppose.

    Would pull plugs and check your gaps.

  7. #7

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    Quote Originally Posted by LittleredMPS View Post
    I would put odds on the plug gaps being too wide.

    Missfire is a common name for spark blow out.

    Usually this is a problem in high boost applications, but its possible I suppose.

    Would pull plugs and check your gaps.
    Yup, will check plugs once I get a set of feeler gauges!

    BTW, the car runs fun, no idle issues, no spluttering.

  8. #8
    Join Date
    Aug 2009
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    hunter valley
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    Could it have been moisture inside or around the coil packs? being cold n all. This came up in the gen1 when my brother decided to wash down the engine :P.

  9. #9
    Join Date
    Jun 2009
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    Newcastle
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    I know in some engines a cylinder missfire code will set if you hit the rev limit, just a random statement cause I can lol

  10. #10
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    Quote Originally Posted by MPS2NV View Post
    I know in some engines a cylinder missfire code will set if you hit the rev limit, just a random statement cause I can lol
    my wife was driving at the time with me in the passenger seat. She wasn't hitting the rev limit ..im sure of it

    I've never had this happen again. I'm putting this down to a bad batch of fuel.
    Trying to keep it subtle ... | COBB AccessPort | COBB DP | CP-e HPFP | CorkSport TMIC | TurboSmart BPV | Denso ITV22| CorkSport Boost Tubes | SURE Full3 Aeros | SURE REM (Street) | SURE AGS SS Shift Knob | 2XS SSP + SURE CounterShift | Speedline Front Strut Brace | Whiteline RSB | Prima Paint Protection

  11. #11

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    Just got the same code. Just after filling up at Shell in Daylesford.

    I've cleared the code and car run fine. I'm guessing country town have had the V-Power sitting there for a while


    Peter "SLIXX"

  12. #12
    Join Date
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    Quote Originally Posted by slixx View Post
    Just got the same code. Just after filling up at Shell in Daylesford.

    I've cleared the code and car run fine. I'm guessing country town have had the V-Power sitting there for a while


    Peter "SLIXX"
    Yeh it happens to me everyone I fill up out of town
    Member Of a Wallbangers Club

  13. #13
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    Jan 2013
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    Quote Originally Posted by naasif View Post
    my wife was driving at the time with me in the passenger seat. She wasn't hitting the rev limit ..im sure of it

    I've never had this happen again. I'm putting this down to a bad batch of fuel.
    The wife and kids
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  14. #14
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    May 2009
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    I had it once. Was about half way through a tank. Just cruising, no fast driving. Just randomly came on.

    Cleared it. Never came on again.

  15. #15
    Join Date
    Oct 2012
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    Brisbane Southside
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    Had the same code today, the tank was empty, like 30km to go or something. Car only has 13 000km on it so I too will put it down to fuel. I filled up and I have cleared it. Will keep an eye on it.

  16. #16
    Join Date
    Oct 2012
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    Damn, got this bloody code again. I have filled up with good fuel so it is not the fuel causing it. Stripped the intercooler off, removed plugs, cleaned, re-gapped (not that they were out), used electrical contact cleaner on every connector. Checked the MAF, the sensor on top was a bit loose, could swivel it side to side, not that I think that could cause anything, but I tightened it. Put everything back together and cleared the code.

    I flashed a new map where I have raised the idle rpm's to 750 to see if it might be an idle issue. It did have this funny burble/missing noise at the tail pipe when it was at 700 rpm idle, it is a little better now but not much.

    Do you think that driving with this code would do anything @2XS @SarcasticOne ? I know that certain ECU's will put the car in limp mode but my car pulls full on, no issues with a misfire is notable........
    Cheers

    Grumpy

    Tuned with
    By Alex...........

  17. #17
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    Oct 2012
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    Oh btw, the car is going for the 12 month service on the 14th, if still there by then, then they can look for the problem. I will return the flash to stock next week.

  18. #18

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    Quote Originally Posted by Grumpy View Post
    Oh btw, the car is going for the 12 month service on the 14th, if still there by then, then they can look for the problem. I will return the flash to stock next week.
    Do you have spare plugs?
    To swap over to trial it?
    I have spare coil packs and plugs if needed too.
    Mine had that code when I had a hair line crack in the plug.
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  19. #19
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    Quote Originally Posted by 2XS View Post
    Do you have spare plugs?
    To swap over to trial it?
    I have spare coil packs and plugs if needed too.
    Mine had that code when I had a hair line crack in the plug.
    No I don't have any spares. So far it hasn't come back yet, maybe something I did worked. I am doing about 500km's this weekend so I hope it behaves. If it does come back I will get in touch Troy, then I will start the process of elimination. It is just strange that it throws the code without any indication of a misfire, I suppose the ECU picks it up way before us mere humans can detect it.

    Thanks anyway Troy, if it keeps this up then I will be in touch....
    Cheers

    Grumpy

    Tuned with
    By Alex...........

  20. #20

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    P0300 is not an idle issue. it is a misfire detected in more than 1 cylinder by the sensors.
    air leaks can cause this code so does bad fuel, spark plugs, coil packs. look for cracks in the ceramic part as 2xs has said but being 13 000 kms i doubt it.
    possible carbon build up too if the car is not driven hard enough as it is a direct injection?

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