Thread: Strange engine drivability issue

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  1. #1 Strange engine drivability issue 
    GTP Level Member buickman104's Avatar
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    My car has 207k on the clock. Maintenance is all up to date. A few months ago I started with a weird issue where I would be at cruising speed 40 to 50 MPH and suddenly the engine started feeling rough and I got a vibration from the engine that would lightly even rattle the dash. I let my foot off the gas and then lightly get the rpms back to speed and back to normal. The problem was pretty rare, but started becoming more and more common about 2 weeks ago.

    What I noticed on my aeroforce is that as I am cruising and as the vibration/roughness develops my timing advance drops into the single digits and stays there until i take my foot off the gas. I get 0 degrees of KR throughout this process unless instead of taking my foot off I put my foot down to try to accelerate. Then I get a over 9 degrees of KR. I also have been getting the p0300 code for random misfires. My vacuum lines are all good, played musical coils and ICM is good. The only thing I can imagine is that my fuel pump is dying out as the issue has become more prevalent as of late. I would like to know if any member has had a similar issue or has a better idea of what the issue might be. My worst fear is that I change the fuel pump for an OEM Delco unit and I still get this issue. Please let me know what you guys think.
    2000 Bronze Metallic GTP
    Power :Gen V, 3.6 pulley, 3 inch down pipe, Power log, FWI,and DHP Power Tuner,
    Handling: Vogtland Springs, GMPP sway bars, STBS, 18" Konig backbone, CTS-V Front brakes and GXP rear brakes
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  2. #2 Re: Strange engine drivability issue 
    Turbo is the way to go. BillBoost37's Avatar
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    How are the plug wires? I'd look to see if anything is hitting, that's a pretty easy area to get vibration in based on being in 4th with lockup.
    I drink..so consider that when reading my posts.

    2010 Audi A6 Dual IC's
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  3. #3 Re: Strange engine drivability issue 
    GTP Level Member buickman104's Avatar
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    The plug wires are brand new. I've played with switching them out between my prj and brand new Napa set, with no change. I also thought it might be a vibration stutter. So I have played with the shifter manually putting it in second and 3rd gears and it still does that weird thing with the timing and vibration.
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  4. #4 Re: Strange engine drivability issue 
    GTP Level Member buickman104's Avatar
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    Bump!

    No one has ever had a similar issue?
    2000 Bronze Metallic GTP
    Power :Gen V, 3.6 pulley, 3 inch down pipe, Power log, FWI,and DHP Power Tuner,
    Handling: Vogtland Springs, GMPP sway bars, STBS, 18" Konig backbone, CTS-V Front brakes and GXP rear brakes
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  5. #5 Re: Strange engine drivability issue 
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    Any chance you have a clogged injector?
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  6. #6 Re: Strange engine drivability issue 
    GTP Level Member buickman104's Avatar
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    I thought about that too, but I have been monitoring missfires while driving on the aeroforce and don't get any while the timing is in the single digits. Also took a listen with a stethoscope and they sound fine at idle.
    2000 Bronze Metallic GTP
    Power :Gen V, 3.6 pulley, 3 inch down pipe, Power log, FWI,and DHP Power Tuner,
    Handling: Vogtland Springs, GMPP sway bars, STBS, 18" Konig backbone, CTS-V Front brakes and GXP rear brakes
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  7. #7 Re: Strange engine drivability issue 
    GrandPrix Junkie
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    I've had this before but not on a W-body. Turns out it was a trans issue/shudder. Think the trans was on the way out and it was slipping while shifting up or the T/C was having issues. Never heard the resolve on it other than the guy replaced the trans. I know you said you tried manually shifting it but thought I'd throw it out there.
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  8. #8 Re: Strange engine drivability issue 
    GTP Level Member buickman104's Avatar
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    Yeah, in the back of my mind I had a feeling it was either a trans or a fueling issue. I am not getting any transmission codes. The fluid level is fine and it doesn't smell burnt. Are there any tests or parameters I should be looking at with a scanner to confirm it is the trans?
    2000 Bronze Metallic GTP
    Power :Gen V, 3.6 pulley, 3 inch down pipe, Power log, FWI,and DHP Power Tuner,
    Handling: Vogtland Springs, GMPP sway bars, STBS, 18" Konig backbone, CTS-V Front brakes and GXP rear brakes
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  9. #9 Re: Strange engine drivability issue 
    GTP Level Member buickman104's Avatar
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    Mind you the trans has about 104k on it and was refreshed with all new sensors, 4th gear stuff.
    2000 Bronze Metallic GTP
    Power :Gen V, 3.6 pulley, 3 inch down pipe, Power log, FWI,and DHP Power Tuner,
    Handling: Vogtland Springs, GMPP sway bars, STBS, 18" Konig backbone, CTS-V Front brakes and GXP rear brakes
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  10. #10 Re: Strange engine drivability issue 
    Turbo is the way to go. BillBoost37's Avatar
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    I know the answer. It's a GP
    I drink..so consider that when reading my posts.

    2010 Audi A6 Dual IC's
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  11. #11 Re: Strange engine drivability issue 
    GTP Level Member buickman104's Avatar
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    That's just because most regal guys never rev their engine past 2,500 RPM so they wouldn't even notice the issue.
    2000 Bronze Metallic GTP
    Power :Gen V, 3.6 pulley, 3 inch down pipe, Power log, FWI,and DHP Power Tuner,
    Handling: Vogtland Springs, GMPP sway bars, STBS, 18" Konig backbone, CTS-V Front brakes and GXP rear brakes
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  12. #12 Re: Strange engine drivability issue 
    GTP Level Member buickman104's Avatar
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    Just wanted to update on this issue for the collective forum knowledge. When I bought the car in 2011 I changed the fuel filter. I decided to change it again because my fuel pump was pretty loud.

    The old filter was clogged and now this problem is resolved and my fuel pump is quiet again.

    Spark notes: if you are having some driveability issues and your fuel pump is loud; then change the filter!
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  13. #13 Re: Strange engine drivability issue 
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    I haven't had this problem (yet?) but thank you for updating us! That's a simple solution to a difficult-to-diagnose problem.

    Thanks again!

    P.S. It took me a 4 foot breaker bar with an additional 4 feet of OSHA-approved torque multiplication tube (rusty steel pipe lol) to break my old fuel filter loose back when I replaced mine
    Last edited by komrad36; 03-26-2015 at 12:22 AM.
    1998 Grand Prix GTP. Open cone intake, ZZP downpipe, dogbone flip.
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  14. #14 Re: Strange engine drivability issue 
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    If it happens while at freeway speeds and light throttle it could very well be a ****ty map sensor or dirty or bad maf
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