Idle surge

Discussion in 'The Venerable Q-Jet' started by Golden Oldie 65, Oct 21, 2019.

  1. Golden Oldie 65

    Golden Oldie 65 Well-Known Member

    I've got an issue with a `69 Q-jet where the engine surges up and down at idle. The car is pretty cold blooded but the choke and fast idle work as they should and for the most part the car runs strong but this slow up and down surge definitely isn't right. Any suggestions? BTW, it's on a `69 RAIV GTO so it's at least a close cousin to a Buick. It's only got 12" of vacuum at idle, which isn't out of the ordinary for a RAIV but seems like it could be a little higher. The only thing I know is that everything was rebuild when the car was restored but it's been years ago has never really been driven except around the block a few times.
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Look down into the carburetor with the engine running at idle. See any nozzle drip? Are the mixture screws responsive? Have light springs in the distributor? Watch the timing at idle, is it steady?
  3. Cliff R

    Cliff R Well-Known Member

    Manual trans or auto?

    Does it have the correct carb on it? Part number?

    I've rebuilt/restored thousands of Pontiac carburetors many were Ram Air models. They are specific to the application for the Ram Air units even using different airhorn, baseplates and special calibrations so they would idle and work well with the big cams they put in those engines......Cliff
  4. Golden Oldie 65

    Golden Oldie 65 Well-Known Member

    Well, I haven't spent much time with the car yet. The story he told me was that it was restored a number of years ago and he bought the carburetor from a guy already restored. By who? He didn't know. It is a correct 7029273 carb. It is a 4 speed car. I have not checked the timing so I don't know at this point whether it has light advance springs in the distributor. It does respond to idle mixture screw adjustments. I can't get the car back into the shop until at least mid-week so I can further check into these things. If timing doesn't prove to be the problem then Cliff, I'll probably just remove the carb and send it to you. I know you can fix it because you have done several RAIV carbs for us that are perfect when we get them back. I am the guy who restores all of Chuck Cocoma's cars. This isn't one of Chuck's cars but I know he has your number. Thanks. In the meantime, when I can get the car back in the shop I'll get all the numbers off the carb and post them here.
  5. Cliff R

    Cliff R Well-Known Member

    A 7029273 is an EXPENSIVE carb these days, hopefully yours is the real deal as they never made any Service Replacements for the manual trans carbs, only the auto's.

    When I build or restore a Ram Air carb for the 400 with the RAIV cam I give it some additional idle fuel that is not needed for the RAIII 400 engines.

    It takes apprx 5-7 percent more of this new fuel to really make these engines happy anyhow.

    Haven't talked to Chuck in a while, hope he is doing well. I've downsized my business as retirement approaches. No employees left, so I get to wear all the hats around here these days.......Cliff

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