Alright for my 80th post this week I need to discuss my off idle hesitation. I have worked the past 2 days cleaning up my vacuum lines, redid the timing, dwell, idle screws, speed, pretty much everything under the sun, and everything seems to be stable after hours of driving. The one nagging problem I have is a very very noticable off idle stumble. As soon as I step on the gas from an idling stop, rpm drops very low then jets right back up. And then when you are in drive from about 1,000-1,500 rpm there is a fairly noticable roughness in the running but if I accelerate above that it runs like a champ. Idle itself is quite smooth too, it just that initial off idle stumble that I can't get out. I thought it may be the accelerator pump, maybe had some play it so I took the lever off and turned the nub that contacts the pumprod down about a 16th of an inch. After doing that and retesting, it seemed to have made the stumble worse, almost to the point of stalling. At this point I gave up for the day, but to me that seems like I maybe am getting too much gas off idle. I have been told by 2 different mechanics that it seems like I am getting too much gas. And it also has a pretty noticable gas smell after it has been sitting
awhile, especially overnight. So I am either thinking it is the acc. pump, so I need to readjust it to give it less push. I did also notice that around where the acc. pump goes into the carb, there is SOMETIMES a tiny bit of gas that seems
to have seeped out. Normal or no? I know there has been some threads about off idle, but I read through them and have tried all the suggestions short of taking the damn carb off and cleaning it. Remember this is a freshly
rebuilt carb that I had some issues with in the beginning but I thought had fixed them. I also haven't screwed with the float yet because I really don't want to get into taking it apart again if I don't have to. Please Help! I can feel I am sooooo close to getting this thing running top notch.

 

I also wanted to throw in there that I tested my fuel delivery and that all checks out too. What's going on?!?!

 

do you know what float is in it? is it brass or composite. the black composite ones will soak up fuel and sink if they are old causing the fuel level to be too high. some rebuilders dont change the float if they look good although that is no indication of it being good or not. personally I would buy a new float and make sure it is set to the proper height.

 

I am unsure which float is in there, but I am assuming the composite. I already have a new float, I just didn't want to have to do the whole float thing. But I guess if I want the best performance I can get, it is something I will have to check out. If the float was in fact giving too much gas into the bowl, what symptoms could be manifesting? The leaking accelerator pump? Gas smell? Off idle stumble? All of these thing that are happeneing?

 

it could cause all of those issues if the float is going bad and not closing the needle and seat properly. at idle the engine does not use enough fuel so the level goes up too high. as you take off it could be flooding over for a second but would improve as you burn off and use more fuel. I would also change the needle and seat while you have it open just in case there is a problem with that as well.

 

Help us out here...are you running the stock Quadrajet? After warmup is the choke completely open? Was the idle set with a vacuum gauge? Sounds like your stumble is caused by a rich condition, this is probably not caused by the accelerator pump.

 

Yeah everything was a stock rebuild except for an electronic choke conversion. I had started another thread yesterday after finally breaking the thing down to have a look at the internals and found some nasty stuff. One of the large brass vent tubes was so crimp and knarled that it had virtually no airflow through it. I pulled an old vent off my spare qjet and replaced it. But main issue I found was that the plastic retaining ring on the top of the power piston was obliterated to the point that it had seized up the piston completely. Also one of the primary metering rod tips was bent pretty badly. So I swapped out the whole piston assembly with a spare set, and while I was at it replaced the accelerator pump....the one that was in there seemed very flimsy compared to the one I have out of a rebuild kit. Double checked everything else and put it all back together again. I haven't bolted it back on due to some prior obligations this morning but hopefully this afternoon I will get the bastard back in there and it will purr like a kitten( fingers crossed) I will let everyone know what happens!