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misfire issue

This is a discussion on misfire issue within the General Help forums, part of the LSx Technical Help Section category; so I have been having a misfire P0307 code and I'm at wits end over it. I first thought it ...

  1. #1
    Member shadowsnkx's Avatar
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    misfire issue

    so I have been having a misfire P0307 code and I'm at wits end over it. I first thought it was a bad wire, replaced, cleared code and drove for about 30 miles. Problem returned. Replaced coil. Fine again for about 10- 15 miles and then problem returned. The whole time I have heard a humming form the hatch area but just figured that it was my subs with the radio off. Today I started the car and walked around back to find out that the humming is comming from what sounds like the gas tank. I replaced the fuel system relay and still have the humming. I don't believe that anything is broken in my engine because this p0307 code is at random. (I get the normal feel of a misfiring engine right before it throws the code) I also replaced the fuel filter but it did not help. I am leaning toward my fuel pump going out. I have a 98 formula with 172000 miles. I also read somewhere that the misfire could be caused on cyl 7 due to a clogged cat.

    If I need to replace the fuel pump someone please give me the racetronic part number.

    Any other ideas are welcome!

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    Veteran 0rion's Avatar
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    before just diving in and replacing the fuel pump I would diagnose it as a fuel pump issue. That humming you're hearing is the bearings in the fuel pump. Not good but doesn't necessarily mean the pump is going out. Mine hummed off and on for 2 years and was still humming and working fine when I pulled it out. Hook a fuel pressure gauge up to it and get it to recreate the problem and see what your fuel pressure is doing. Check that #7 injector and make sure it's not clogged. It could be a few different things but I would probably check the fuel pressure and that injector first.

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    Member shadowsnkx's Avatar
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    so none of the junk yards around here will buy my cats. says that its a state law.

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    Veteran 0rion's Avatar
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    look in the parts wanted section....there are 2 guys in there that'll buy 'em.

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    I flame retards CamaroFan71's Avatar
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    They buy old worn out cats??

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    Quote Originally Posted by CamaroFan71 View Post
    They buy old worn out cats??
    yep, as long as they're the oem cats. Junk yards usually will buy them for the platinum that's inside them. That's why people have resorted to stealing the cats off cars.

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    O U 8 1 2 Spaz's Avatar
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    stupid question... have you ever jacked up the trans/engine??? i slpiced my wire from the PCM to the coil pack by accident and slice the 7th cyl wire... i did that jacking my engine up to drop the trans mount... either that or when i lowered the trans down the engine did it then...

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    Member shadowsnkx's Avatar
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    I did change the mount a while back, but I replaced the coil yesterday and did not see a ripped wire on the harness. anywhere else I should look?

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    the cake is a lie twozs's Avatar
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    crank sensor?

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    Member shadowsnkx's Avatar
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    Checked fuel pressure. Its between 55-60 psi. Will check the crank sensor tomorrow as well as check the cyl compression. I took the plug out and it had some gunk on it. the beige area is now brown. all the other plugs look ok. Removed the cats today as well.

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    Member shadowsnkx's Avatar
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    So my dad thinks that I have a bad valve seal. Half of the spark plug has a black gunk on it. We placed a dollar bill by the left tail pipe and it tries to suck it in after a few rotations. He said that this is a indication of a bad valve setup. Any thoughts?

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    Member shadowsnkx's Avatar
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    So I removed the intake and injectors. #7 cyl injector was clogged so I used some carb cleaner to get the gunk out. Looks like coffie grinds. All the rail holes had it built up. I flushed the line from the filter up and man...... a ton of that shit came out. I'm working on getting it back together and I will try it then!

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    The car is running great now that I cleaned the injectors by hand. Funny thing is that I am not getting the hiss from the fuel pump anymore. Thanks for the help guys

  14. #14
    Veteran 0rion's Avatar
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    glad you got it worked out.

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    We'll be back... GatorSS's Avatar
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    I suppose you never or rarely ever used fuel injector cleaner?

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    Member shadowsnkx's Avatar
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    cleaner

    Quote Originally Posted by GatorSS View Post
    I suppose you never or rarely ever used fuel injector cleaner?
    Well I just bought the car.lol

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    Ok guys. After a few weeks with no issue, I was driving to work this morning and got the p0307 code again. I have a feeling that its the same problem. I have a 98 with the steel gas tank so could the tank be rusting and causing this to happen? If so is there a drain plug on the tank so I can try to get most of this stuff out?

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    O U 8 1 2 Spaz's Avatar
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    Quote Originally Posted by shadowsnkx View Post
    Ok guys. After a few weeks with no issue, I was driving to work this morning and got the p0307 code again. I have a feeling that its the same problem. I have a 98 with the steel gas tank so could the tank be rusting and causing this to happen? If so is there a drain plug on the tank so I can try to get most of this stuff out?
    your fuel filter sohuld be catching that stuff if that is the case... could be the element in the filter breaking down??? when was the last you changed it???

  19. #19
    Veteran 0rion's Avatar
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    yeah, pull your fuel filter and see if dirty gas pours out of it. You may just have some build up in the rails or something that's breaking loose and clogging the injectors. Get it cleaned out again and run some fuel system cleaner through the car. I pulled my tank a year or so ago and there really wasn't much in the tank to be concerned with and mines a 98 also. Check that filter first if it has many miles on it then go from there.

  20. #20
    Member shadowsnkx's Avatar
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    I changed my filter when I first had the problem a few weeks ago. Maybe I should change it again. I used seafoam in the tank before I changed the filter the first time. maybe it has broken the stuff down and the filter is letting it pass?

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