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Idle problem, misfire and backfire

This is a discussion on Idle problem, misfire and backfire within the General Help forums, part of the LSx Technical Help Section category; My car has a slight miss at idle. Backfires occasionaly. Also when I push the clutch in the idle will ...

  1. #1
    Member afattitude's Avatar
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    Idle problem, misfire and backfire

    My car has a slight miss at idle. Backfires occasionaly. Also when I push the clutch in the idle will not go down for several seconds and will not go down at all when i have any speed. I did the !AIR and !EGR and put breathers on the valvecovers and a catch can where the EGR was. Is there something wrong with the EGR somehow? A code possibly? Or could the fuel pump or regulator have gone bad? I am getting a P0300 code so it is not just one cylinder.

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    Senior Member Redphoenix1998's Avatar
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    Did you get a tune after the mods?

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    Member afattitude's Avatar
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    Nope haven't had it tuned yet. But i have had the lid and the exhaust on before and never had these problems. It wasn't until the
    !EGR and !AIR and me puting the LT back on that this began.

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    Senior Member Redphoenix1998's Avatar
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    Since it's a random misfire, check your fuel pressure. The Reg is build into the sender unit in the tank and rarely goes bad so I do not suspect that too much. Take a stethoscope and check each injector. Injectors don't throw codes. You need to manually check to make sure they're ticking away. Take a spark tester and check each coil via the wire and tester. Clean your MAF. Just go through all that to try to hunt it out. But in all honesty, I'm thinking you just have to delete the EGR and AIR from the PCM.

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    FASTER THNA SPEEDINtICKEt BANDITO's Avatar
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    On mine it was a loose and melted plug wire. maybe plugs wires or 02 sensors.

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    Member DaddySS's Avatar
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    Can you post some pictures of the engine bay, especially the catch can and EGR set up?

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    Veteran 0rion's Avatar
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    also, check for leaks where you plugged the egr hole in the intake manifold and the exhaust manifolds for the egr and air. Sounds to me like you're getting some extra air in there somewhere.

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    Senior Member Redphoenix1998's Avatar
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    Yeah, vacuum leak is a good place to start as well.

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    Member fieropope's Avatar
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    wouldnt the untuned computer be trying to compensate for the "filler" that the EGR would be letting into the intake and when the filler isnt there your a/f ratio be incorrect??just a question but i belive that would be your problem might as well get a tune anyway

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    Senior Member Redphoenix1998's Avatar
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    Veteran 0rion's Avatar
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    no, there's only a spark adder table for the egr you have to worry about. I'm gonna guess as to why....exhaust is almost completely depleted of oxygen which is why there's no airflow adjustment necessary when pulling the egr. That's a guess but it makes sense to me. I just know you don't have to account for the airflow but you do need to adjust the timing tables or you'll get some tip in knock retard.

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    Hide ya kids Hide ya wife 94ss06gxp's Avatar
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    x2 on the timing tables.. sounds like something is messing with timing

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    Veteran 0rion's Avatar
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    Quote Originally Posted by 94ss06gxp View Post
    x2 on the timing tables.. sounds like something is messing with timing
    I don't think it's a timing issue...sounds like a vacuum leak to me.

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    Member afattitude's Avatar
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    thank you everyone for all the great info I guess I'm gonna start looking tomorrow of what is issue is. Thanks again!!

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    Veteran 0rion's Avatar
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    good luck. When you find it post back and let everyone know what you found. Might help someone else down the road.

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    A burned O/2 sensor wire will cause some issues like that. After putting the LT's on, its not common to have ran the extentions or the long wire somewhere it got burnt. Happend to me exactly like that.

    Good luck!

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    Member afattitude's Avatar
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    Wow, found a wire that somehow found a way to touch the EGR that I blocked off. I knew i should have bought it without those provisions!! Also the Rubber blockoff that was in the top of the intake seemed to be starting to squeeze out like a jelly doughnut so i loosened it and stuffed it back down and ratcheted her tight. Also looking around to get the catch can setup right cuz apparently the way I had it was letting unmetered air into the system. Purrs like a kitten now. Thanks everyone!

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    glad you got it up and running

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    What he said ^.^

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