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  • Misfire and code PO300 advice needed

    Hey guys, it’s been a while since I have posted, but I have run into a bit of trouble and I was hoping someone could give me some advice. My 1999 V6 Camaro (stock 3.8, approx. 116,000 miles) started sputtering while driving the other day and is giving me a code PO300, which indicates a Random/ Multiple Cylinder Misfire. I went under my hood and decided to check the connections on my coils, and right off the bat, I found that the plug wire boots on the first coil (cylinders 6 & 3) were sitting up higher than they should be - in other words, they were not pushed all of the way down. This is very odd, because me and the car repair shop that I used last (the ones that I had a falling out with because their tow truck damaged the front end of my car when they towed it to the shop) had to be responsible. I know that I didn’t do it, so it had to have been them.

    Anyway, so I pulled the boots off, and right away I see rust and corrosion on the electrodes. So I think, there’s the problem, but something inside of me was saying “if only it was that easy”. Well, I took the coil off and I clean the electrodes of all of the rust, clean out the plug wire boots with electronic cleaner spray and Q-tips, and coat everything with dielectric spark plug boot protector grease. Then, I put everything back together, and of course as I was expecting, I still have the same exact problem.

    So then, I check to see if I am getting any spark from the coil, and it does not have any spark on either electrode. The middle coil (for cylinders 5 & 2) is sparking like it’s supposed to. I didn’t check the coil on the inside (cylinders 4 & 1), because if it wasn’t sparking, I don’t think that the car would be running at all. I even tried three spare coils that I have and even borrowed a coil off of my son’s 2000 Malibu to see if it could be that my coil had gone bad, but none of this worked. I also checked the voltage coming into the coil from the ignition module, and I was getting 25 volts (AC) on the right side terminal using a bolt on the fender well for ground. Now, this is what I don’t know - what is the voltage coming in to each coil from the ignition module supposed to be? I would think that it should be more than 25 volts. Is there not a possibility that if a misfire runs long enough, it can cause the ignition module to go bad? Also, does anyone know if there are any fuses or relays that could be the culprit?

    Thanks in advance for any help.

    Bruce
    Last edited by ONLNTM5A; 04-13-2008, 01:03 PM.

  • #2
    Re: Misfire and code PO300 advice needed

    Update: I have put a new ignition control module from Advance Auto and I had to replace one of the coils as well, because the guy at Advance messed up one of them while checking it. He was using paper clips to put into the plug-in slots on the bottom of the coil and then couldn't get it out without messing it up, so he gave me a new after market coil (BWD brand). The other two checked good (they are GM OEM replaced about 8,000 miles ago). Both parts that I replaced today, the coil and the ignition module are "BWD" brand. I am now getting the first coil (6 & 3 cylinders) to spark, whereas it didn't before I replaced the ignition module. In fact all of the coils are sparking now. The only problem is, that I still have the same problem and still getting the PO300, "Random/ Multiple Cylinder Misfire". So, I still don't know what to do with it. The plugs and wires were replaced about 10,000 miles ago with GM parts, but I have a feeling that there may be a possible problem with either a plug wire(s) or carbon build up maybe on plugs 6 &3?

    Anyway, hopefully someone will come along and have an answer for me soon.

    Thanks,
    Bruce

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    • #3
      Re: Misfire and code PO300 advice needed

      I'm no expert and I'm not entirely sure but if your plugs weren't firing couldn't some fuel probably foul them up? I'd replace the suspected plugs on any cylinder that had any problems to at least eliminate a possible problem.

      TEAM C6V6

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      • #4
        Re: Misfire and code PO300 advice needed

        you should just do your plugs and wires. it doesn't cost that much and it's worth a shot. could you have burned a wire or to also?
        WAWA-A-HOLIC

        Comment


        • #5
          Re: Misfire and code PO300 advice needed

          Thanks for the replies - I have read all of the posts that I could find on the internet about this subject (here's a good thread http://web.camaross.com/forums/showthread.php?t=78028)
          I am definitely thinking that it could be plugs and wires at this point -

          Comment

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