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NOT TRUCK!!! OLDSMOBILE CAR ?'s

Discussion in 'Chevy Trucks' started by BrendonV, Mar 12, 2003.

  1. BrendonV

    BrendonV Junior Member
    Messages: 15

    I know this is a Chevy Truck discussion but i dont know who else to ask.......

    1984 Oldsmobile with a 4 barrel carb., car starts right up but starts to choke out while idleing and continues to choke and spews black smoke from exaust while idleing considerably well. Does something need to be adjusted to eliminate this from choking out???


    BrendonV
     
  2. wyldman

    wyldman Member
    Messages: 3,265

    Sounds like the choke pulloff is bad or not set-up right.It is a small vacuum chamber with a rod to open the choke slightly after the engine starts.On most q-jets,it's at the pass side front of the carb.There is a small phillips spring loaded screw to adjust it.

    Check to see if it holds vacuum,if it doesn't replace it.If it does hold vacumm make sure it's adjusted right,and the linkages are free.It should pull the choke open about 1/4" when the engine starts.
     
  3. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    Ditto what wyldman said,the front choke pull off is most likely bad.To check it just pull the vac hose off,make sure it has vacuum,plug it back in it should retract and pull on the choke linkage.if it doesnt retract the diaphram is bad,replace the pull off.
     
  4. BrendonV

    BrendonV Junior Member
    Messages: 15

    my dad replaced the choke pull of, and all the vacuum hoses are attached.....he wanted me to say that when he took out the plugs they were so bad it wouldnt start with them and they were so black... if that helps....
     
  5. johngus

    johngus Senior Member
    Messages: 117

    check for the choke plate opening after the car starts.It should open a little when first started,thats the vacuum pulloff,after that the choke should open all the way slowly,thats the choke thermostat.if the pullofffs working but the choke still is not opening fully check for 12V at choke stat,if 12V present the choke stat is bad.
     
  6. wyldman

    wyldman Member
    Messages: 3,265

    like johngus said,see if the choke plate comes open a bit when you start it.If not,then maybe the new choke pull-off needs adjusting ? or the linkages are binding ?

    If the choke plate comes open a bit,and does not come all the way open when the cars warms up,then the choke cap may be bad or unplugged.

    One other thing could be a stuck float.Gently tap the carb bowl at the front near the fuel inlet,and see if it gets better.If it does,then the float may have collapsed,or stuck,or the needle and seat are not sealing.
     
  7. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    Stuck floats are extremely rare on quadrajets. Much more likely is the float bowl vent cannister went bad. Id wedge the choke plate linkage open,then if it still doesnt smooth out. remove the air cleaner base,and in the front of the carb,there is a good sized 3/8" at least line going into the top,its the float vent.Remove this,and just leave it unhooked for teesting purposes,ifit smooths right out,the bowl vent valve is bad. This is an emissions control device,so you may need to get it at your dealer, if this is bad,id leave it unhooked until you get one.When they go bad,engine vacuum will pull fuel right out of the float bowl,and pull it thru the vacuum lines.The car will run extremely rich when its doing this.
     
  8. wyldman

    wyldman Member
    Messages: 3,265

    That's wierd John.I have found the exact opposite in my experience.With the reduced capacity fuel bowls (due to strict emission standards) and larger floats,they are more prone to sticking.The q-jet body is also very prone to warping or distortion,caused by improperly torquing the air horn to carb body screws,and the carb hold down bolts as well.Sometimes retorquing everything will fix it.

    Good point on the bowl vent,I have seen a few do that as well.
     
  9. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    Wyldman,i have worked on ton of Qjets,never had one stick a float,could it be our fuel additives? Anyway the warping is defintely a big Qjet problem,as is loose throttle shafts one hi mileage ones.The bowl vent valve is very common here,by the time they bring it to you,usually the plugs are wet,the cat is plugged,and theres a quart of gas in the oil :D .
     
  10. wyldman

    wyldman Member
    Messages: 3,265

    It may be the difference in emission control setups as they are quite different from Canadian to US cars,and vary from region to region.We see the throttle shaft problems too.In fact it's getting hard to find good rebuilable cores.Been converting a lot of our older Chev's over to Holley's,as they are cheap,and easy to tune,just never work quite as well as a good q-jet.