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308 2Vi Sputter...

Discussion in 'Technical Q&A' started by desire308, Apr 17, 2008.

  1. desire308

    desire308 Formula 3

    Oct 19, 2007
    1,433
    Florida
    Full Name:
    Peter W
    Here's what I changed; New oem wires, extendors, boots and changed to a hotter plug [NGK5 vs the NGK6 I had prior]. Moved to an 89 octane fuel from 91/93 [premium]. I read here somewhere that the 308 should run fine on 89 octane.

    I have a sputter on acceleration...say 3000-4000K and then it's gone. Never above...it runs very strong. Also idles fine.

    Where would you start?
     
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  3. bocaspyder360

    bocaspyder360 Karting

    Jan 18, 2008
    128
    TRY HIGHER OCTANE SEE IF IT GOES AWAY
     
  4. desire308

    desire308 Formula 3

    Oct 19, 2007
    1,433
    Florida
    Full Name:
    Peter W
    I'm leaning towards this...tonight it ran like crap and even dieseled when I shut it down.
     
  5. 335s

    335s Formula Junior

    Jan 17, 2007
    869
    SF Bay Area
    Full Name:
    T. Monma
    Is the EGR vacuum value set properly?
    Ck your intake tract for vac leaks, you are describing what appears to be a lean misfire in the progression stage from "idle to mains"-only this is a K-Jetronic car!
    If the plate is bouncing in the housing due to pulses, this will cause some problems(see EGR above).
    Since this fuel is closer to being alchohol than "true" gasoline(2,5 isopentane, probably...), your octane rating is reflective of the fuel's principle qualities with respect to ANTI DETONANTS-NOT any inherent increase in "btu" content....it does NOTHING with regards to power. Period.

    You have incomplete, and or, improper flame front.....
     
  6. desire308

    desire308 Formula 3

    Oct 19, 2007
    1,433
    Florida
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    Peter W
    Pulled the rear bank plugs...2 are carbon fouled.
     
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  8. desire308

    desire308 Formula 3

    Oct 19, 2007
    1,433
    Florida
    Full Name:
    Peter W
    Pulled front bank plugs...all normal. Appears I am not getting proper spark at the rear bank [unless above 3500 rpm]. Tried a new ground for the ECUs and swaped same...no change. Re attached the coil wire at the distributor to assure good contact. No change. BTW...all new wires. Wonder if this is a flywheel sensor going bad or poor contact? Bad rotor?
     
  9. desire308

    desire308 Formula 3

    Oct 19, 2007
    1,433
    Florida
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    Peter W
    Please chime in here...I want to get her running right ;)

    Strange how this all occured doing simple proceedures and trying different gas...as one other said here..."if it ain't broke, why fix it"

    Just like to keep ahead ;)
     
  10. Gianluca

    Gianluca Formula Junior

    May 6, 2003
    349
    Centreville, Virgini
    Full Name:
    Gianluca Chegai
    I had a similar problem and replaced the flywheel sensors (all 3 but 2 were good) and it runs like a charm.
     
  11. climb

    climb F1 Rookie

    Sep 19, 2006
    4,694
    Atlantic Beach Fl
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    Stuart K. Hicks
    Maybe try the original plugs. New ones but original model #.
     
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  13. desire308

    desire308 Formula 3

    Oct 19, 2007
    1,433
    Florida
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    Peter W
    Changed back to colder plugs, put in a full bottle of octane booster and baam! She's humming again.

    It's 93 octane from this day forward [she told me so].

    Who said the 308 runs fine on 89???

    Not true, at least in my case.

    Perhaps the PO modified the car...hmmm.
     
  14. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    17,188
    USA
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    Hugh G. Rection
    Never heard of a 308 running on less than 91 octane. Also, the NGK 5's are only recommended on the carb cars, and even then, the 6's often work fine. The injected cars should all be on 6's or 7's.
     
  15. desire308

    desire308 Formula 3

    Oct 19, 2007
    1,433
    Florida
    Full Name:
    Peter W
    Well...you live and learn...now this is engraved in my brain ;)

    And again...it's amazing how crappy they run on less than 91.
     
  16. jon s

    jon s Formula Junior

    Mar 9, 2005
    509
    pocasset ma
    Full Name:
    jon shoukimas MD
    been running my 81 on 89 ron for 4 years without any gas related problems. if it doesn't detonate on load you have adequate octane rating. think how low the stock engine compression is on these engines. and i believe that now that all new cars are injected there's no longer any big difference in the amount of cleaner by grade of gas. i think you probably have a slight mixture problem or weak spark. on the other hand if the problem vanishes with higher octane i wouldn't spend hours trouble shooting. regards, jon s.
     
  17. Meister

    Meister F1 Veteran
    Silver Subscribed

    Apr 27, 2001
    5,384
    Duluth, MN
    Full Name:
    The Meister
    In my 8 years of ownership I've run both 87 and 89...not an issue. I rarley if ever go 91+
     
  18. desire308

    desire308 Formula 3

    Oct 19, 2007
    1,433
    Florida
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    Peter W
    This is pretty clear based on what happened. It was either the hotter plugs, a slightly loose connection on the ECUs or the gas...I lean towards gas since it cleared up "as I drove" with the booster in the tank. I guess time will tell.
     
  19. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    17,188
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    Hugh G. Rection
    Probably a combination of plugs and gas. The test would be to go back to 89 on the next tank and see what happens. As far as additives in gas, a neighbor of mine works for Shell, and confirmed there is a higher concentration additive package in their Premium or V-Power as they call it. But even their regular and mid grade exceed the federal standard and meet the new "top tier" industry standard.

    http://www.shell.com/home/Framework?siteId=us-en&FC3=/us-en/html/iwgen/shell_for_motorists/fuels/fuel_stretch/fuel_stretch_fuels_ga_0111.html
     
  20. desire308

    desire308 Formula 3

    Oct 19, 2007
    1,433
    Florida
    Full Name:
    Peter W
    Could be...it continues to run fine, better at temp.
     
  21. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    17,188
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    Hugh G. Rection
    Could have simply been the colder plugs fouling, causing the miss.
     
  22. desire308

    desire308 Formula 3

    Oct 19, 2007
    1,433
    Florida
    Full Name:
    Peter W
    I had the BP5ES plugs in the car when it was fouling...showed up on the rear bank...then replaced them with the originals the PO had in the car which were colder, re-checked the ECU connections and added booster to the 89 octane gas in the tank. After about 10-15 minutes of driving it cleared up.
     
  23. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    17,188
    USA
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    Hugh G. Rection
    Sorry, I misread your original post. Too hot a plug can cause pre-ignition, which may be what you were experiencing.
     

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