Running rough after manifold r&r | FerrariChat

Running rough after manifold r&r

Discussion in '348/355' started by Headrips, Jun 21, 2011.

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  1. Headrips

    Headrips Rookie

    May 24, 2010
    49
    Orlando
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    Scott
    #1 Headrips, Jun 21, 2011
    Last edited by a moderator: Sep 7, 2017
    Hi guys I've replaced a coolant union under the manifold on the crosspipe...that was corroded in half...luckily found it while I was cleaning the MAFs, and not on the highway!.....I removed and replaced the manifold/plenum as per the awesome write ups found here....While I was at it, I removed the injectors and sent them out for testing/service. I got it all back together, and the car runs fast and strong, but has an uneven idle, sort of like one bank is out of sync with the other.......loping sound is hard to describe, any ideas? Any help would be appreciated before I have to eat crow and take the car to my tech!
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  2. race850i

    race850i Karting

    Jan 6, 2010
    132
    Germany
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    Themis
    Its getting air somewhere in the Manifolds.
    Check your work again,it might be a gasket or a rubber seal faulty.
     
  3. Headrips

    Headrips Rookie

    May 24, 2010
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    Thanks for the tip, will recheck!
     
  4. PAP 348

    PAP 348 Ten Time F1 World Champ
    Lifetime Rossa Owner

    Dec 10, 2005
    100,220
    Mount Isa, Australia
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    Pap
    Definitley sounds like a vaccum leak mate. Check all manifold bolts are tight and you put all hoses back on. :)
     
  5. Headrips

    Headrips Rookie

    May 24, 2010
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    Thanks guys ....I did notice that the manifold lifted right off of the gasket with no effort, so I didn't bother replacing it ....there was no evidence of sealant, so I just put it back on and torqued it down.....should I try sealing it with rtv?
     
  6. sws4re

    sws4re Formula Junior

    Jan 28, 2006
    281
    Olathe Ks
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    Scott Sweat
    No rtv. Pull it back apart and replace the gaskets. You dont want to suck any of that down the intake.
     
  7. PAP 348

    PAP 348 Ten Time F1 World Champ
    Lifetime Rossa Owner

    Dec 10, 2005
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    Before pulling back apart mate, get some carby cleaner and spray around the base of the manifold.

    If the revs pick up back to normal, then you know it's sucking air there. Worst case, spray carby cleaner around everything you pulled apart one section at a time to check for vacuum leaks.

    If you understand what I am saying.
     
  8. plugzit

    plugzit F1 Veteran
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    Dec 1, 2004
    7,776
    Redondo Beach, CA
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    Bruce Bogart
    What Pap said.
    Did you mess with the linkage? If the TBs get out of sync, it'll do that.
    Vacuum hoses can get confused or not hooked back up (especially the one under the manifold going to the equalizer valve).
     
  9. Headrips

    Headrips Rookie

    May 24, 2010
    49
    Orlando
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    Scott
    Thanks guys! Will try the carb cleaner test, and recheck all the vacuum hoses tomorrow...I'm assuming that I should spray the carb cleaner around these areas while the engine is running and look for a smoothing out of the idle.........
     
  10. Headrips

    Headrips Rookie

    May 24, 2010
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    Orlando
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    Scott
    Thanks guys! Will try the carb cleaner test, and recheck all the vacuum hoses tomorrow...I'm assuming that I should spray the carb cleaner around these areas while the engine is running and look for a smoothing out of the idle.........
     
  11. PAP 348

    PAP 348 Ten Time F1 World Champ
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    Pap
    Yes sir! :):)
     
  12. Headrips

    Headrips Rookie

    May 24, 2010
    49
    Orlando
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    Scott
    OK, carb cleaner test was inconclusive, but after checking all hoses my gut tells me to tear it all back down and replace the manifold gaskets....anyone have part numbers? I wasnt able to find them on Ricambi........

    Also, while I was in there, I noticed a patina of old gunk on the valves and inside the manifold chambers (with the manifold upside down)....I'm not about to take the heads off, but is there anything that is safe to spray on the valves that will loosen /clean that stuff off?

    Thanks again
     
  13. PAP 348

    PAP 348 Ten Time F1 World Champ
    Lifetime Rossa Owner

    Dec 10, 2005
    100,220
    Mount Isa, Australia
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    Pap
    You would want to be 100% sure before pulling the manifold back off mate. :D:D

    Check it over again. ;);)

    Subaru makes an EXCELLENT "top end" cleaner. Buy some of that and follow the instructions.

    Basically you have the car running, bring the revs up, remove a vacuum hose from the plenum and spray this top end cleaner in there.

    Most times, you will see a puff of black soot out the back of the exhaust as it burns off the crap from the back off the valves. Doesnt get it all (depending on how much crap is on them I guess), but it also loosens the other crap off and it eventually gets burned off.

    It's that good!!! We use it alot, costs around $40 for a small spray can here.

    It cleans the back of the valves so they seal better. We have seen instant results like a smoother idle and up to 2 hp extra on the dyno. **Both different cars**
     
  14. Headrips

    Headrips Rookie

    May 24, 2010
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    Scott
    Ok will recheck and retorque on Sunday, is there a torque specification on the manifold bolts? Don't wanna go too gorilla on those aluminum parts!
     
  15. Headrips

    Headrips Rookie

    May 24, 2010
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    Thanks Pap, And I'll give the subaru stuff a shot thanks for the tip, which vacuum line/port would you recommend using for that treatment?
     
  16. PAP 348

    PAP 348 Ten Time F1 World Champ
    Lifetime Rossa Owner

    Dec 10, 2005
    100,220
    Mount Isa, Australia
    Full Name:
    Pap
    Cant help you there sorry mate. :)


    Whichever one. Drop off any hose there that has vacuum, there should be a few there. :)
     

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