Momar

Sometimes the car will kind of do a little stumble usually at lower speeds and not very much throttle at all though. It will do it idleing too. If you look at the exhust it gets a slight puff of black smoke when it does it like it is getting too much fuel. It seems like it might be running a bit rich anyway too. The carb is off of an 84. My cousin and I just built it for his car and then his comp died and he decided to use a non computer carb and dist he had so I got this. It ran fine on his car and did pretty well on mine at first, but later in the same day I put it on mine it started doing this and the ilde is a bit rougher. What do I need to do?

Thanks

Ben

Momar

Anybody. If you need more details, just let me know what you need and I will tell you.

Thanks

Ben

83_1/2 L69

You might have a loose electrical connection at the M/C sol. That would cause the carb to go "full rich" intermittently.

Momar

I dont think thats it. It only does it when at very light throttle. If I push the throttle down a bit more it goes away. It didnt do this with the other carb I just took off. I think that something is probably not adjusted right, but I dont know what it would be. It smells like it is running rich at idle, but I have the dwell at ~30 degrees. I also have noticed that the motor doesnt want to start unless I touch the gas where as my other one would start by just turning the key. Is this a symptom of the fuel leaking out and I need to epoxy those 2 spots(where are they by the way) or is it something else?

Ben

yanfoo

I had that exact problem, wich i think its solve now.

-Car would crank forever to start (bowl empty my guess) and needed me to tap the pedal.

-After a while parked, if i started it, i had a cloud of smoke wich smelled fuel. not black, but i have a cat, do you?

-One rough idle, shake shake shake, shake your booty, la la la!


I epoxyed ALL! of the plugs inder the bowl piece... (the middle one)


So what you want to do is take the carb off, and remove the 2 LONG screw on top, and 2 screw underneat the throttle piece.
you need to remove the PV rod and the choke rod... i think thats it...

I did all of the plugs, 2 big , 2 small , but you'll see the others, they have the same caps as the 2 small one... wich you can see when the carb is fully assembled, they look like eye. hehe
I did not do anything else than put epoxy on it, just made sure it was all dry. seem ok. not pretty.

if my carb turn out fine, i'll be able to put my hedders WOOHOO!!
just like your 2210. there at the coating shop right now.
Then im on the hunt for the best price on spintech.

Momar

I dont have cats. Can plugging these help the rough idle at first or just the having to hit the gas pedal to start? So do you not have yours back together yet? If you did did it fix your prob? What kind of epoxy did you use. I like the headers a lot, and if I get a chance to run the exhaust out the back I will probably switch to spintechs also but it sounds bad *** with the bullets too.

Ben

phess11

I used JB Weld on my plugs.

Momar

I will probably fill those plugs in the near future(hopefully next weekend) I dont think that is my running problem though. I have been doing some searching and I think I have what was referred to by five7 as an off idle flat spot. It is worse before it hits closed loop. I didnt have it with the other carb that was on there either. I havent been able to find what kind of adjustment to do on a cc qjet to fix this though.

Ben

phess11

Make sure that your MCS travel is at least 4/32. I set mine to 5/32.

Momar

How exactly do I do that? I think that I have the lower limit set to stock, but I thing that the upper might be further down from when I set the iab to get the dwell to 30*. Actually, the iab isnt the upper limit, but rather where it starts between the limits isnt it? I need to know specifically what to measure and how to set it if you could because I only somewhat understand how these carbs work.

Ben

phess11

The IAB adjustment will not change the travel of the MCS. The MCS has a Lean Stop (bottom of the MCS travel) that should be set on a carb rebuild, and a Rich Stop (top of the MCS travel) that should also be set at rebuild. Both adjustment screws are located top/center/front of the q-jet and have plugs over them.

Momar

I believe we punched those out when we rebuilt it but what do I need to set them to?

Ben

Momar

And will I need a special tool?

Ben

Skip Fix

If the carb sat for a while the accelerator pump seal probably dried out. The accelerator pump should have a steady squirt to smooth the transition off idle when you give it gas. there are two different holes that the linkage can go in that change the speed of the squirt.

Off idle circuits also undergo "power enrichment" as the power piston spring moves the primary rods out of the jets to a smaller part of their taper. This can get tweaked in a rebuild sometimes, also different springs are avaialble to play with. Edlebrock makes a mumber of Q jet products new.

Momar

The accel pump seal is new. When I took the carb off I found that it the front bolts had lossened up and the front of the gasket was soaked in gas like it was leaking so that could have played a roll in my origional problem. I just put it back on after epoxying what I hope was the plugs everyone talks about(2 big 2 small). Anyway, I put it back on and it seems to be running good at part throttle, but is idleing at 1000 now. I think that they throttle may not have been returning clear back to the idle screw but it was at least close. I will check that. Also it is now a dog. I think I did something to the secondaries some how when I had it out. It bogs now when get on it off of the line instead of throwing you back and at when you are at speed and get on it it just feels mushy. I had the carb upside down so I think I will check to make sure that the rods are still on the hanger but I didn’t change any adjustments so I don’t know what happened. I haven’t had the scan tool on it since I put the carb back on tonight. My vacuum caps were messed up so I just have vacuum lines on it with screws in them until I can get new ones(as of tonight) so do you think that could cause the problems I am having now(high idle and bogging) if I have a vacuum leak. My cousin is supposed to get me tool so I can adjust the rich and lean stops so I may mess with that a bit if I can find specs.





Ben

Skip Fix

Two other things to check. The vacuum hose to the secondary vacuum break(dashpot on the front passenger side) it as well as the spring on the secondaries control the opening of the secondaries. Too quick and a bog. The spring is set with a screw locked in place by an allen or Torx head screw rear passenger side of carb. 3/4 turn past were the flaps just seat is a good starting point.

The primary and secondary well plugs are the ones that were prone to leaking but mainly on the pre 74 Q jets. A dab of Devcon or JB weld on each will prevent that.

Q jets need a good return spring to pull the throttle back on the idle screw. Also the choke fast idle cam if on at al will make it idle up. My son's 81 Trans Am the spring had stretched and it idles al lover the place til I put a new one on.

Momar

Well, I messed with it some tonight. I found where my bog was coming from. It appeared that I had tightened one of the back screws that goes clear from the top of the carb clear down into the baseplate to tight. When I opened the av flap manually it stuck. I loosened the screw and it poped shut and didnt catch any more. Unfortunately even though the bog was gone the car wasnt as fast as when this carb was on before I jbwelded those plugs. I still havent figured that out. Could a vacuum leak cause this because I think that I might have forgot to plug in the line that goes to the flaps in the air cleaner. I was thinking about it and doesnt that t off of the spot where the secondary vacuum break is? If so I would think that it would give me a bog instead of the throttle just feeling "mushy" like it did. I also want to pick up some vacuum caps because right now I have the ports I am not using pluged with vacume lines with screws in them because my vacuum caps got torn up moving them back and forth from carb to carb. I could possibly have a vacuum leak in one of those but dont know.

Anyway, on to the primaries. I checked and the mcs only had about 1-2 mm of travel and it is supposed to have 3.9 mm. I have that carb off so that I can work on it sometime this weekend and get everything at least set to spec so I can go from there. I noticed that I couldnt really get the dwell to go below 40* no matter what I did.

Off topic but I raced a 96 cobra today. I lost. I already switched the carbs and this one is the one that has been slower all along. I think that I have the av tension to loose on it because it was bogging real bad tonight. I think that if I would have had the other carb on and the secondaries working as well as they were last weekend I would have been able to beat him though. It just doesnt have near the pull with this carb as it did last weekend when I beat the LS1 z28 running the other carb. I just cant figure out what I did unless to the secondaries I just didnt have a vacuum line on because I didnt adjust anything. All I had done was take it off epoxy the plugs, let it set 24 hrs and put it back on and it was dog slow. I cant wait to get this straightened out and go have some fun.

Ben

Skip Fix

There is a guy in that part of the country named Cliff Ruggles that is prepping alot of Q jet for Pontiac guys. He even likes the mid to late 70s ones. I can get you an address if you can't get it figured out. Be sure there isn't so much epoxy the baseplate isn't seated well on the body and is causing a vacuum leak the gasket can't seal.

Momar

No, there really wasnt all that much epoxy at all. Anyway, I am going to try to get the rich and lean stops set right today and see how it does from there. I am also going to try to get some vacuum caps instead of the hoses with screws in them. I am hoping that the secondaries was just because I didnt have that one wire hooked up.

Ben

Momar

Ok, I think I have the secondaries working right but I still am having trouble with the primaries. I checked and had to little travel on my mcs. I set the lean stop to 3 1/2 turns out per the instructions with a rebuild kit I had. I then bottomed the rich stop and then put it back down a 1/4 turn. I now appear to have about the right amount of travel. The problem is that I am getting a rich code. I have the idle mixture screws out 7 turns. Currently the iab is out 4 turns. I did a search and was reading through some posts and got to thinking that I am not sure that we set the float level when we rebuilt it. How do you do that and could it cause my problem? Do you think I should just try lowering the lean and rich mixture screws or leave them where they are at. I am almost to the point of just buying a remanufactured one, but wont probably have the money for a couple weeks so that gives me some time to get this fixed and decide not to first. I got new vacuum caps and replaced the vacuum line to my secondary vacuum break, just to try to eleminate some possible vacuum leaks. I just want it to run good. Any suggestions welcome.

Ben

phess11

I had a similar problem with my q-jet. It turned out that 7-turns out on the Idle screws was too much. I ended up with 3-turns out and the IAB is almost to the top. Before I did that the dwell on the MCS was fixed at about 50. Hang in there you'll get it.

Skip Fix

Float levels are critical in Q jets. too low and off idle tranisiton circuit do weird stuff. I'd double check the factory specs. Some guys use as high as 1/8", got to watch for slosh at the secondary rods then on hard acceleration. I want to think my second gen one is around 11-13/32.