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vacuum leak

Discussion in 'Engine/Tuning' started by 04oxfordvert, Sep 1, 2019.

  1. 04oxfordvert

    04oxfordvert Member Established Member

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    so my car idles rough at best when it has 15 in hg. then will drop to 10 and slowly stumble then die. cannot find leak in engine bay. this is all stipped at an idle. the crazy thing is while at cruising 60mph and close theottle completly it will jump to 20-22 in hg. im totally stumped. any ideas. checked pcv all is good and all lines in engine bay are good..

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  2. Bdubbs

    Bdubbs u even lift bro? Established Member

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    Hopefully it's not the pcv hose in the lower intake. I'm kicking myself for not at minimum putting a hose clamp on that hose when I swapped blowers.

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  3. 04oxfordvert

    04oxfordvert Member Established Member

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    im pretty sure its not that as i pulled the pcv out and there was major vacuum there. so im kinda ruling that out. and i was affraid of that aswell. lol
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  4. slo984now

    slo984now AKA 01yellerCobra Established Member

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    What throttlebody are you running? Does it happen all the time or only at certain temps? Such as cold start or when the engine is fully warmed up.
     
  5. 04oxfordvert

    04oxfordvert Member Established Member

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    i have a 2.3l tvs gt500 tb setup. doesnt matter cold or hot. and it just started doin this in past 2 days. have driven all summer no issue.
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  6. hotcobra03

    hotcobra03 Well-Known Member Established Member

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    Are you running cats

    Clogged exhaust was my friends issues It shows low vac at idle than drop
     
  7. 04oxfordvert

    04oxfordvert Member Established Member

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    no cats. arh lt to or x.
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  8. hotcobra03

    hotcobra03 Well-Known Member Established Member

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    Another area.

    Intercooler orings.

    Any lose of coolant?
     
  9. hotcobra03

    hotcobra03 Well-Known Member Established Member

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    Intercooler housing gasket also.

    Strange some have said they don’t have a gasket in another thread
     
  10. 04oxfordvert

    04oxfordvert Member Established Member

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    no loss of coolent. intercooler is pumping well.
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  11. 04oxfordvert

    04oxfordvert Member Established Member

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    there appears to be 1 vacuum line that runs into the passenger fenderwell that runs along side the evap lines and im not sure where that one leads to.

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  12. hotcobra03

    hotcobra03 Well-Known Member Established Member

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    Google the link.
    It brings you back to svt here. You want the second pdf.

    03cobra vacuum hoses documented

    Is a pdf file. Shows all lines with color pics
     
  13. hotcobra03

    hotcobra03 Well-Known Member Established Member

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    15 is low with out cams.

    Have you done a compression test ?

    I drove many miles on 7 cylinders

    1 valve
     
  14. 04oxfordvert

    04oxfordvert Member Established Member

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    ya but at highway speed with throttle closed i get 20-22. its only at a stopped idle. it makes no sense. and i will google the routing
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  15. 04oxfordvert

    04oxfordvert Member Established Member

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    it appears from that diagram that the hose in the fender goes to an evap vale mounted in the inner fender. im gonna see if i can get at it. as i have zero tools as im moving accross the country. lol but that could prob have an effect on low vacuum and possibly a fueling issue?

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  16. hotcobra03

    hotcobra03 Well-Known Member Established Member

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    Fender well cover needs to be pulled down.

    Has plastic push pins

    And screws on rocker panel corner

    Where is your gauge attached

    There isn’t really much vacuum on this car

    And with the huffing and puffing I can see a gauge do strange things
     
  17. hotcobra03

    hotcobra03 Well-Known Member Established Member

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    That lower intake hose is the biggest hose of the system.

    I did clamp my hose after seeing
    171/174
    Hose got hard and wouldn’t pull off nipple yet it would spin on nipple which was a major vacuum leak

    It’s like the evap. Hose that makes your hand black and not come off.

    Items that should be replaced with new fuel line hose
     
  18. 04oxfordvert

    04oxfordvert Member Established Member

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    ya i seen that thats where it is. my guage is attached on a tee behind the glove box on the yellow hose.
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  19. 04oxfordvert

    04oxfordvert Member Established Member

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    ya ive verified that hose is good as pulling the pcv out there was major vacuum. ive ruled out that and the hvac lines. the evap and vlack hose that gets you black are only 2 left to verify.
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  20. hotcobra03

    hotcobra03 Well-Known Member Established Member

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    You can’t rule out lower intake hose with out removing lower intake for hands on nipple in face

    Actually it’s always good to clean intercooler

    It only takes a few minutes to pull blower and intake
     

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