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  • OBD II trouble code P0300

    I no longer have a clue what is causing my misfires. I went to Autozone and got my car diagnosed. They said it was code P0300. I DID search this in the archive, and all it says for code P0300 is "Engine Misfire Detected". I am pissed because this is all I have to go on to figure out what is wrong. I have replaced wires, plugs, coils, everything short on the ignition module. I would like to think that is not the module, but I am leaning towards that because it is the only thing I haven't replaced yet. If anyone has a clue about the code or what is wrong, let me know.

    Wes
    1995 Pontiac Firebird
    2008 Chevrolet Silverado LT Crew Cab 4x4

  • #2
    This might sound strange, but check the cat.

    A friend of mine had one that was completely clogged up and the insane amounts of back pressure were causing misfires at speeds above 70 MPH.

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    • #3
      I had the same thing happen to me. My cat was getting clogged and throwing off misfire codes. It got so bad it wouldnt rev past 3 grand and autozones ODBII detected multiple random missfires.

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      • #4
        Another thing to try would be to change the fuel filter and add a can of STP Complete Fuel System Cleaner to a full tank of gas. This cleared up a P0300 problem I had in my Olds Ciera. I spent quite some time troubleshooting it - did the wires, coils, even the ignition module - but the problem was just a crapped up fuel system.

        For the paltry sum of $15, it's worth a try.
        ...it\'s lonely out in space...

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        • #5
          anyone thought of the fuel pressure regulator? I had this problem with my car and I've had two sets of plug wires and new plugs before they finally found the cause. My cat also shelled out because of that darn regulator too. Just an idea.
          Nitrous is like a hot chick with an STD....you wanna hit it, but you\'re affraid of the consequences...<br /><br /> <a href=\"http://www.cardomain.com/member_pages/view_page.pl?page_id=244935\" target=\"_blank\">http://www.cardomain.com/member_pages/view_page.pl?page_id=244935</a>

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          • #6
            The fuel pressure regulator was what I suspected on my car (see above) after eliminating all possible ignition related problems. Since I didn't have a pressure guage to test it, I decided to try the filter and fuel treatment first, and it worked. But it is true, a bad regulator (or even a bad fuel pump for that matter) can cause similar problems. What I think happened in my case was that the filter was so clogged, it was affecting fuel system pressure. Since the car is MPFI, it did not exhibit the characteristics of a clogged filter that I was used to seeing with older TBI-equipped cars (complete stall, unable to restart for a few minutes, etc...)
            ...it\'s lonely out in space...

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            • #7
              I didn't think to check the cat. I might do that.
              I usually run fuel system cleaner through the car after every oil change. But the idea of the regulator also gets me thinking.

              Thanks guys [img]smile.gif[/img]
              1995 Pontiac Firebird
              2008 Chevrolet Silverado LT Crew Cab 4x4

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              • #8
                <blockquote>quote:</font><hr>Originally posted by Mogobs30th:
                I no longer have a clue what is causing my misfires. I went to Autozone and got my car diagnosed. They said it was code P0300. I DID search this in the archive, and all it says for code P0300 is "Engine Misfire Detected". I am pissed because this is all I have to go on to figure out what is wrong. I have replaced wires, plugs, coils, everything short on the ignition module. I would like to think that is not the module, but I am leaning towards that because it is the only thing I haven't replaced yet. If anyone has a clue about the code or what is wrong, let me know.

                Wes
                <hr></blockquote>

                ok... same here... 96 camaro... i replace plugs, wires and coils... 2k miles ago i redid my ENTIRE exhaust system so i know it's not the cat... what else could cause this.....
                <b>*§*Julian*§*</b><br />*~*~*~<br />2000 Grand Prix GTP -Daytona 500 Edition (only 2000 made) - Supercharged 3.8L V6<br /><br />1998 3.8L V6 A4 Firebird w/ W68 package, Y87, T-TOPS!<br /><br /><a href=\"http://myweb.usf.edu/~jadidona/index.html\" target=\"_blank\">MY SITE - CHECK IT!</a>

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                • #9
                  I haven't had a chance to check the cat or regulator, but if it isn't one of those, then the only thing I can think of is crossfiring. I'll have to check that tomorrow.
                  1995 Pontiac Firebird
                  2008 Chevrolet Silverado LT Crew Cab 4x4

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