need help with 2001 monte carlo SS

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Thread: need help with 2001 monte carlo SS

  1. #1
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    need help with 2001 monte carlo SS

    The car has 47,000 miles on it. 3.8 liter engine. It has allways run great till 2 weeks ago. I change oil religiously, and change air and fuel filter when needed. The problem is this, it runs good at idle and up to 3500 rpm then at 3500 to 4000 rpm it stalls and wont go any more. starts to slow down, looses all power but is still running. when I try to push accelerator to floor it starts to misfire and engine light comes on with a code of misfire. I here something like a click under the hood like the computer shutting something down causing it to do what it is doing. then when you let off the accelerator you can here the click again and the motor starts running fine again. until you get up to 3500 rpm again. right at where it wants to change gears driving normal. I cant figure out what is going on. I changed the fuel filter just to rule that out. fuel pressure shows 59 psi when key is turned on pump pressuring system. when pump cuts off pressure shows 50 psi. when I start car and it is idling it still shows 50 psi. when i hit the throttle it will go up to 59 psi then start to go down. what i mean by hitting the throttle is pushing throttle down a little then letting off. I changed the fuel pressure regulator just to make sure that wasnt it at $50.00 and some change. because the pressure did not drop 3 to 10 psi from pressure at key on fuel pump off wich was 50 psi. actually it should have been 53 to 59 psi key on pump off but it does go to 59 when you first turn key on and pump is pressuring system. and again after it is started and giving it throttle it will go to 59 psi so I am sure fuel pump is okay. problem is the same, does anyone have an idea as to what it can be? I need help, cant figure this out. If it were plugs or injectors it would run bad at idle on up to 3500 but it runs fine to there then wont go any higher. any help would be appreciated.

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    6.2 Liter LS9 Supercharged V8 MrCritical's Avatar
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    Re: need help with 2001 monte carlo SS

    Check engine light?

    Fuel pressure is correct.
    Last edited by MrCritical; 11-30-2008 at 12:27 PM. Reason: added info.

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    Re: need help with 2001 monte carlo SS

    check engine light only comes on when I push accelerator to floor and keep it there. engine wont go over 3500 rpm it just back fires quietley if that makes sence. the code when I check it shows engine missfire.

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    Re: need help with 2001 monte carlo SS

    any mods?

    what's the missfire code?

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    Re: need help with 2001 monte carlo SS

    did you check the volume of the fuel pump? as far as how much fuel its getting, not just pressure.
    There are no stupid questions, just stupid people.

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    Re: need help with 2001 monte carlo SS

    There are no mods done to car. The code is PO305 had it checked at auto zone. it says PCM has detected that a misfire has occured in cylinder #5 how do I check the volume of the fuel pump? Thanks for everyones help in advance, I would like to try to fix this without having to take it to a mechanic. the warranty just ran out a few months ago. and am short on cash right now. I would think since the computer seems to be shutting it slowing it down after 3500 rpm there would be a code for it. but there is none. I would not even be getting the misfire code if I never held the pedal to the floor. It takes about 5 seconds of the pedal on the floor to get the engine light to come on.

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    Re: need help with 2001 monte carlo SS

    as far as fuel, I think it is getting plenty. when I took the pressure regulator off I relieved the pressure first through the pressure gauge. and some how it still had pressure, cause when I took the spring clip off and went to pull the regulator off I know more than got the clip off and the regulator popped off and gasoline sprayed me in the eyes and face like I never even relieved the pressure. I mean it forced it into my eyes. I was blinded till I made it into the house and found the kitchen sink then washed my eyes out and face off. Man that burned. I mention this only because it may have something to do with what is wrong with the car. If not feel free to laugh.or not. wont do that again any time soon I hope.

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    Re: need help with 2001 monte carlo SS

    My first and el cheapo guess is that your #5 plug wire is breaking down. Replace it with another AC/Delco wire.

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    Re: need help with 2001 monte carlo SS

    Thanks, I will get some new wires tomorrow and replace them all. will post when done to let you know if it helped.

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    Re: need help with 2001 monte carlo SS

    to check the output of the fuel pump you need to get specs for how much its supposed to put out as far as volume, cant tell ya what the specs are, but if its low on volume you will be low on fuel to the rail. which is common at higher rpm. so it could very well be a fuel pump issue. just because pressure is good doesnt mean that the volume is good. check it by getting a container, and seeing how fast it fills it up. there is a spec for it, just need to find it.
    There are no stupid questions, just stupid people.

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    Re: need help with 2001 monte carlo SS

    changed plug wires today, and looked at the plugs. They look like they ought to. car still running the same, if not alittle worse. I like the old cars, the ones you can work on. and everything is easy to get to.

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    Re: need help with 2001 monte carlo SS

    Why would low fuel volume cause missfire on one cylinder?

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    Re: need help with 2001 monte carlo SS

    because it does it at a certain rpm. if it is a cylinder related problem then it would do it at all times.

    personally, i think there is more to it. no offense to autozone, or who ever scanned it, but i think there is more to it than just that stuff, hence more problems than just a misfire on #5, it probably isnt picking up the other misfire codes, or any other codes for that matter. like say a tech 2 would. its just too bad you dont have access to a tech 2. then you could look at misfire data, and fuel trims and other vital information. as well as o2 sensors.

    a random misfire at certain times doesnt spell out a direct problem just on that cylinder.

    and if it were a coil pack then more than likely it would do it on the opposing cylinder as those packs each fire 2 cylinders. its hard telling what the problem is.

    as i said, just check the volume of the pump, just to make sure its flowing ok. its easy, just unhook your fuel line from the rail and key on engine off the fuel pump.
    have a container ready, you may have to do it a different way as they only spray for a couple seconds. there will be detailed instructions in service info for the procedure.

    all im saying here guys, is that if its just a single cylinder misfire we are dealing with, dont you think that the car would run half way decent? the way he describes it, it sounds like it just falls on its face. and it does it at a certain rpm. i mean we are dealing with a 3.8 liter hear, not a 4 cylinder. so a single cylinder misfire isnt going to exactly bring that engine down on power as bad as he describes.
    Last edited by Triple-X08; 12-01-2008 at 06:25 PM.
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    Re: need help with 2001 monte carlo SS

    I checked the coils and all show okay. I have not checked the volume of the fuel yet, since the last time I messed with something on the fuel rail {fuel pressure regulator** I got sprayed in the eyes with fuel even after releiving pressure. I clear the codes and still come up with #5 misfire. problem is getting worse, is messing up throughout driving range. I am beginning to think intake plenum also. I would like to think a car with 47,000 miles on it would not have problems like this. It is just broke in. I have 76,000 on my 2004 silverado and have never had any problems. runs great and have not had to give it a tuneup or anything. I would sell the monte carlo, but daughter wants it. I hope she still wants it after I have to take it to be fixed. cause if she wants it she is paying for it. I have about had it with this car.

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    Re: need help with 2001 monte carlo SS

    take some carb cleaner and spray around the intake plenum to see if it increases in rpms or runs better or worse. if it changes, it has an intake leak.

    spray at the base of the plenum. i just find it odd that a plenum would cause a misfire on one cylinder, and not a entire bank, or multiple cylinders.
    There are no stupid questions, just stupid people.

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