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  • engine idle issue

    On Thursday I picked up 93 Firebird with the 3.4L V6 with an auto tranny (wish it was a stick) that has 160K KM on it (100K in miles), and it seem likes a good car except for one issue. When the car is in park it idles fine, but then I put it on drive and I’m at a stop about 75% of the time it starts to idle a little rough. The engine fluctuates between 600-500rpm, it idles at 600rpm in park. After it idles rough and I start to accelerate the engine runs rough (has some hesitation) till about 1,300rpm and then it runs fine. Also I have noticed that when the car is in park and I rev it high then promptly let off the gas it lightly backfires. It almost feels like the gas isn’t burning right and when I step on it the engine needs to clean out the chambers. Here’s what I’ve looked at till now. Cleaned the mass air sensor which ended up being dirty, this made the car run smoother but didn’t fix the issue. Checked one of the plugs which looked clean and was an NGK platinum series. Checked the throttle positioning sensor and it was only giving me a 4.25v reading when the throttle was fully open. I read that it should be throwing 4.5-5v at this point so I replaced the TPS sensor (forgot to check the voltage since). My next step is to pull all of the plugs this weekend and look at them to see if they’re all clean, then double check the plug wires (they’re 7.5s) which I have a bill saying they were recently replaced. After that I was going to look at the oxygen sensors, the engine light on the dash is not on. I just wanted to see if I was on the right track and also see if anyone else has had this problem and could help me.

    Also what are some cheap mods that I can do to get more power out of the 3.4L V6, I hear you can typically pull some more power out of these engines easily.

    Thanks.

  • #2
    Check the fuel filter as well. With that many miles, if its the original, it'll help starve the engine of fuel quite easily.
    -Brad-
    89 Mustang : Future 60V6 Power
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    Follow the build -> http://www.3x00swap.com/index.php?page=mustang-blog

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    • #3
      Originally posted by bszopi View Post
      Check the fuel filter as well. With that many miles, if its the original, it'll help starve the engine of fuel quite easily.
      I forgot to also mention that the fuel filter was recently replaced too, or atleast it's on a bill. Thanks for the note though, I'll make sure it was replaced and atleast replaced with the right one.

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      • #4
        Even though the plug wires have been replaced, I would still be sticking my nose in that direction if I were you. It's misfiring in the same manner as my Corsica was misfiring and when I replaced the plug wires it completely cured it.

        After that, if you're going to pull out the plugs anyway, go ahead and replace them with AC Delco platinums. Cheap enough and good insurance. I replaced my first set at 190,000 miles and they were still working fine.

        Good luck and let us know how it's going!

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