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P0300 misfire WTF!!!

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Old Jul 16, 2005 | 02:41 PM
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Default P0300 misfire WTF!!!

Ok guys i need help BAD! I was driving my car from Abilene TX to Houston and after I got about 50 miles from Abilene my car started bucking. I thought i was running on 7 cyclinders so i pulled over and checked the wires. (changed spark plus the day before i left) After i fired the car back up and took off it started bucking again and the SES light was flashing at me. SO i call the mach. and he tells me to baby her home, well about 100 miles from houston, It stops and the car runs fine. SO while i was in houston i bought some MSD wires to hope clear the problem. NOPE! On my way back to abilene it started doing it again 100 miles from houston, when just cleared right up! I stoped and got gas, when i fired it back up got to 3rd gear and the car started doing it again. It was throwing the P0300 code. I have no idea whats going on or how to fix it. Please help!!!!1


Mods are MTI C2 cam (224) pacesetter lts, hptunner, no cats, slp loudmouth, MTI lid and its a 01 Z

Mike
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Old Jul 16, 2005 | 03:06 PM
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maybe you have a bad spark plug or something, that would freak me out. i am very precausious about my car and any sounds or anything like that hope you figure it out.
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Old Jul 16, 2005 | 03:09 PM
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how many miles on your plugs?
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Old Jul 16, 2005 | 03:20 PM
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600 miles
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Old Jul 16, 2005 | 04:45 PM
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ttt mike
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Old Jul 16, 2005 | 06:46 PM
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Have you checked your valve springs yet? A broken one will throw a miss code P0300...
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Old Jul 16, 2005 | 09:03 PM
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Originally Posted by Matt@HSW
Have you checked your valve springs yet? A broken one will throw a miss code P0300...

No i havent, but it doent do it all the time (missfire)
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Old Aug 1, 2005 | 11:00 AM
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Have you checked your valve springs yet? A broken one will throw a miss code P0300...
Please don't scare me
I just put in my F10 cam with new Patriot Duals, and I'm getting this code.
It was resetted, but comes back anyways.
If it was a broken spring I would definitely feel something wrong...shaking, or lack in performance, right ?

I think I'll start with some more typical things,...wires, connections....etc.
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Old Aug 1, 2005 | 11:26 AM
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Did you tune your PCM recently or is it stock? My car did the same thing as yours and it was a bad PCM.

You would probably know it if you had a broken valve spring...
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Old Aug 1, 2005 | 12:35 PM
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Is your SES light flashing or you're just throwing that code? Has you PCM been tuned? It's normal for a cam car that has not been tuned to throw that code. It's not normal for that code and a flashing SES light. The flashing SES light indicates a current misfire.

Matt


Originally Posted by AdamSS
Please don't scare me
I just put in my F10 cam with new Patriot Duals, and I'm getting this code.
It was resetted, but comes back anyways.
If it was a broken spring I would definitely feel something wrong...shaking, or lack in performance, right ?

I think I'll start with some more typical things,...wires, connections....etc.
Reply
Old Aug 1, 2005 | 01:02 PM
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It sounds like the P0300 started shortly after the plugs were changed...assuming no other changes were made, and no instances of P0300 before the plug change, that's the likely culprit.

You already took care of my first recommendation, the plug wires. Very possible to damage the ends during a plug change, either pulling out the crimped-on end or loosening it to the point that it doesn't make solid contact w/ the plug or coil.

Go over the plug wires once more, pushing and twisting to ensure they're clicked into place securely...be paying attention to see if you get any clicks, which indicate the wire was loose.

If no success there, I'd swap plugs. Either put the old ones back in, or grab another new set.

Inspect the plugs you just removed for cracks on both the interior and exterior porcelean, variation in the gaps (you did measure the plug gaps when you installed them...didn't you?), or other signs of trouble.
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