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  1. #1 vacuum leak and missfire codes 
    GrandPrix Junkie SgtMarshal's Avatar
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    my gtp has been hesitating under heavy acceleration. yesterday it tripped two codes P0171 P0300. how do I know how much vacuum I should have? I have an aeroforce scan guage that I can scan with but im not sure what it should be showing. any other help is appreciated
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  2. #2 Re: vacuum leak and missfire codes 
    GrandPrix Junkie Bluemagic's Avatar
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    Vacuum should be 19-21 I believe.
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  3. #3 Re: vacuum leak and missfire codes 
    Turbo is the way to go. Fivefingerdeathpunch's Avatar
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    Setup the aeroforce to read MAP in/hgs, and see where its at. Should read around -19 to -20.6 at warmed up idle.

    I would do a spark plugs and wire change if you never have aswell, would be easy things to do, to try and get rid of the misfire code.

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  4. #4 Re: vacuum leak and missfire codes 
    GrandPrix Junkie SgtMarshal's Avatar
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    I ran the engine until the coolent tempurture was showing 180 to make sure it was warmed up and at idle it was showing -14.2. I did the gen 5 swap 3 weeks ago so im wondering if it has something to do with that.
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  5. #5 Re: vacuum leak and missfire codes 
    GT Level Member Erik Adam Rodriguez's Avatar
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    get carb clener and spray aroung the lim
    02 grand prix gt- L67 swap, ZZP 1.0 pcm, thrasher CAI, SLP 2.5 catback, A/C delete, 02 emulator, poly dog bone mounts, 6000k projectors with CCFL halos, 12 in slotted front rotors, ported blower and intake, evap and EGR deleted, 12" kicker cvr with 1000 watt amp, alpine cda 9886 deck
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  6. #6 Re: vacuum leak and missfire codes 
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    check the t fitting under the sc snout and the egr valve metal tube that goes to the lim... those are the most common and could also cause p0300 but i would also listen to fivefinger about the plugs and wires
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  7. #7 Re: vacuum leak and missfire codes 
    GrandPrix Junkie SgtMarshal's Avatar
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    I confirmed it is a vacuum issue. the fitting on the supercharger that you are supposed to run a vacuum line to the throttle body had a cap on it. so the supercharger had increased crank case pressure. I took the cap off and cleared the code and it hasnt come back, so if I understand it correctly the fitting is acting like a breather for the supercharger until I run the vacuum line.
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  8. #8 Re: vacuum leak and missfire codes 
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    ok you lost me there??? did you just uncap the fitting and leave it open or did you add the necessary vac line to the throttle body??? because uncapping a vaccuum fitting will not act as a breather and if its after the maf sensor itll cause issues...
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  9. #9 Re: vacuum leak and missfire codes 
    Killa Bee Scottydoggs's Avatar
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    i think hes talking about the pcv valve was capped off, and not ran to the TB like it should be. its a gen 5 swap deal.

    and trust me i had to re read it 2 times to come to that conclution lol

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  10. #10 Re: vacuum leak and missfire codes 
    GrandPrix Junkie SgtMarshal's Avatar
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    the fitting im talking about is on the backside of the supercharger and im pretty sure that its the one I need to run a vacuum line from and connect to the throttle body. I just havent gotten around to taking the throttle body off to drill out the brass plug and install a fitting so I can install the vacuum line.

    does that make more sense?
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  11. #11 Re: vacuum leak and missfire codes 
    Killa Bee Scottydoggs's Avatar
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    yup pcv is on the rear of a gen 5 blower. and hooks to the TB.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  12. #12 Re: vacuum leak and missfire codes 
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    ah i understand now thank you
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