Thread: O.K. you quadrajet gurus

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Roadster pickup with stock 85 small block 305 and quadrajet has been fired for first time since massive clean-up and installation from donor car.---All vacuum ports plugged on q-jet except one at rear side which went to power brakes originally-(now is plumbed to pcv valve). starts good, runs well in mid range , but will only run with choke 3/4 on at idle---stupid carburator either doesn't have idle screws, or has them sealed from factory. What do I do now ???? Don't suggest get new carburator---no money for that luxury. There must be something I can do , I just have no idea what.---on an older 4-barrel, I would have monkeyed with the idle screws untill the thing would idle without choke, but on this carb that don't appear possible.--I can put a new needle and seat in, and set the float height, but that appears to be the limit of what I can do----HELP!!!!!

I remove the hardened idle mixture plugs by turning the carb upside down and with a cut off wheel carfully make a cut about an 1/8 inch from the end off the plug cross wise. You will initially be cutting into the aluminum base. Then I place a punch in the grove I created and tap the plug out. Be care full, when you hit the plug there will be sparks. Make sure ther is no fuel in the carb to catch fire.
It sound like there may be a vacuum leak or a plugged Idle curcuit. I think all '85 quadrajets off cars are feedback types that require special tools to set up.
Hope I'm being helpful

I think I know where denny is going with this. Some quads were sealed from the factory so there were no adjustments, technically. However, you can drill holes and get to the air/fuel adjustments. I don't know if this is the same quad you have, but the year is about right. If I were you I'd get him those pics so we can all see what's going on here.

Unfourtunatly the plugs are hard so you can't drill them. The carb kits say to use a hack saw and cut the baseplate on either side of the plug and use a chisle to remove the material around the plug.

Anytime your working on a Quadrajet be sure that you use the Barker Un-warping Tool and the Barker Throttle Shaft Bushing Kit in-order to insure that your carb. will work correctly when your done.

A gentleman from another hotrod forum has suggested that my problem may be that I used the large vacuum port on the back of my carb, which used to operate the power brake booster on the donor car , to operate my pcv line. He says that the vacuum canister for the power brakes is actually a sealed canister, and that what I have done is creating a huge vacuum leak. He may be right, because I never had the center head off this motor, only the carb, and I know that my gasket is good between the carb base and the center head. The engine idled fine in the donor car before I cleaned everything up and swapped the vacuum lines when I transplanted the motor.. Denny is right, the carb needs a gasket set and a new float, needle, and seat.---I hope the fellow is right about the vacuum line---I will try plugging it tomorrow and see what happens. I don't really want to mess with the idle adjusting screws if I can avoid it.

Brian, there are a few diagnostic tricks you can do with a newer Q-jet. First of all, try pluging the port going to your pcv. Sounds odd, but trust me on this. 2nd, all Q-jets past 82(?) are feedback style. As such, the TPS will throw the entire carb out of whack. You have the option of a voltage test, or simply unplugging the carb for a few seconds and hitting the throttle once. If it stumbles, the TPS is good. if it does nothing else and runs the same, grab a throttle position sensor. thats the white(maybe gray/black) three prong connector on the right side of the carb. To replace it, youll have to lift the top off from the carb. Finally, there is a mixture solonoid on the left side of the carb in the front. Many times these will stick due to rust/bad gas/other fun contaminants. The easiest way to get ahold of this is to open the carb and spray it liberally with carb and choke cleaner. then manually move the solonoid free. Finally, in order to get ahold of those screws, try a cobalt or titanium bit. they ARE drillable, but drain the carb complelty and be carefull. Good Luck

Ooooh, ouch. I was under the impression he had the Q-jet that came with the motor. Nevermind.

He may very well have the one that came with the motor. Depending on the make many did not have the electric carb until '85, '86. I know because I have owned several of the same year cars with different carbs from the factory. The books may try to tell you one thing, but don't let them kid ya. They sealed them puppies up from about '80, '81 and not all had TPS's until about '86 then most went TBI.

As far as drilling goes, you are correct. We usually drill them. The hacksaw trick does sound a bit safer though. I gotta admit.

Success!!!!! It seems that the gentleman who said not to use the power brake vacuum port to my pcv set-up knew what he was talking about. Today, without changing anything else, I put a pair of vice-grips on the hose and clamped it shut. The car fired right up, and after about 5 minutes warm up, seems to idle much better on its own, without me having to blip the throttle at all. Denny is definately right, in that it needs a gasket and float kit, but it appears that is all it may need. This is something brand new to me---I never heard of this before, but hey----it worked. Now all I have to do is figure out what port to use for the pcv. There is a large vacuum port on the front of the carb that used to go to the charcoal canister---I have it plugged right now, but it can easily be unplugged and used----any opinions????

Okay, it sounds like a bad PCV valve. Did you hook the breather line to the air cleaner or leave it open? It also will effect the PCV.