See if you can figure this one out:

The engine stalls out under 900ish rpm.

1) It's basically a stock crate 350 with quadrajet and stock HEI.

2) i've got EGR and a whole mess of vacuum hoses and whatnot (i will try to get a picture up ASAP).

3) i replaced the vacuum advance canister, but no improvement.

4) the engine starts easy, and after it stalls, it is easy to start.

5) the engine runs ok at rpm's above 1200ish. Maybe slightly rougher than normal, but basically ok.
a) the trans, however, seems to take alot longer to upshift than before.

6) it does not matter if in gear or not, and it makes no difference wether i'm coming to a stop sign or not----in other words, this happens in neutral regardless if the car is moving or not.

7) This condition just started about 5 days ago. It ran basically ok before that; It would idle in gear at 500rpm.

5) the engine runs ok at rpm's above 1200ish. Maybe slightly rougher than normal, but basically ok.
a) the trans, however, seems to take alot longer to upshift than before.

This is Just a guess, but have a look at the transmission vacuum modulator rubber hose for leaks.
It should run from the vacuum tree on top of the intake manifold behind the carb and run down to the modulator on the rear of the trans.
It may have a metal tube part of the way but the ends are normally rubber tubing and can perish.
Check the PCV, booster, EGR and any other vacuum hoses for leaks if that's not the culprit.

The vacuum modulator's rubber hose seems ok. In addition, the vacuum modulator itself is good, (or assumed to be good for purposes of this thread for now) as i replaced it 2 yrs ago. Also, there is no white smoke from the exhaust pipes.

The vacuum hoses all seem ok, but i have thermal vacuum switches and ported vacuum switches (which i believe vacuum advance is running off of). Again, i will try to get a picture up asap. i will test the switches as soon as my vacuum tester arrives.

P.S.
8) If i keep the throttle up and keep the engine running at more than 1000rpm, the engine will run all day. (but you probably could deduce that) It's only if i let off of the throttle (regardless of in gear or not) that it will run rough and stall out.

9) The distributor has not moved----i could not move it by hand. So, i think we can safely assume that the timing did not retard.(?) i originally set the initial timing at 8deg BTDC, if i remember correctly, which should be ok for the relatively mild cam.(?)

i'll add more pertinent facts as soon as i remember them.

What i'm basically trying to do is gather all tools and any/all possible causes. And then organize all potential causes and test them all. i have also ordered a factory service manual along with a vaccum tester.

get a can of carb cleaner with the plastic ext get someone to keep it running for you at lowest idle you can and spray a round base of carb and a round vac lines if you have a broken hose or gasket the idle will get higher when you do that and check egr valve reach your fingers under and push up it should change idle or stall it may not be seated good or you can do it with vac pump hand held

I originally set the initial timing at 8deg BTDC, if i remember correctly, which should be ok for the relatively mild cam.(?)

I'm not saying this is the problem, but your initial timing @ 8" BTDC is too retarded for anything but a stock (low HP) cam.
16* initial will make it idle better, but you may need to limit your total to around 36* without vacuum advance.
The symptoms you're describing are typical for a vacuum leak.

1) What is generally happening, with some luck, is that when the engine is cold i can generally get the engine to continue to run---albeit just barely; i think this has something to do with the fast idle cam?
So this would allow me to run over to the front and eventually, if nessesary, keep the engine running by moving the throttle by hand. In this way, i can try the carb cleaner thing.

2) i don't think the timing is the problem right now, in that the engine ran and idled just fine until last week. However, i agree that the 8 degrees is very probably too retarded and i will definitely advance it as soon as this other mess is over and taken care of.

So anyways i changed the pcv valve----because it needed changing anyways because it's been on there since i got the truck and it's only $2.95 anyways. A little improvement but really the problem is still there; It may not stall out anymore but the idle is still rough to the point where the engine is barely running at 600 rpm. i think if the engine really got warmed up, it would very probably revert to stalling out.



Next, we get to the EGR valves.

By the way, the service manual came in and it is fatter than 2 phone books. And the manual was saying that there are 2 types of EGR. How do you tell if you got positive or negative feedback EGR?

i took this one off the engine for inspection:

http://i223.photobucket.com/albums/dd31/sencraig/100_0412-1.jpg

This other one, i took off the 305 i have sitting in the garage for comparison:

http://i223.photobucket.com/albums/dd31/sencraig/100_0413-1.jpg


a) for the top one, the one off the truck, i was able to push the diaphram in and if i kept my finger over the vacuum supply opening, the diaphram would stay inwards until i took my finger off and then the diaphram would move back to resting position.

3) How do you test the vacuum advance canister? i've read that you move the lever to the most advanced position and put your finger over the place where the vaccuum hose would connect and it, the lever, should not move until you release your finger? Suprisingly, the manual, says nothing about testing vacuum advance, or at least i'm unable to find it.

4) i should also mention that when the engine is "idling", or doing it's best attempt to "idle," the vacuum gauge swings broadly all over the gauge in rhythm with the engine.

You dont wait to get the carb fixed before the timing,you always need to get the timing right 1st.

As already stated your motor likely needs at least 16 deg base timing and 8 deg is way too retartded if thats the case so take 5 mins to get that right 1st ,then go after carb etc.

From your vac gauge reading ocilating at idle it sounds like it could be timing and also weak or incorrect springs in the mech adv causing an unstable/ocilating idle.

You can try installing stiffer mech adv springs to see if that helps or changes the unstable idle ,if no change put other spings back in but if a chage for the better with stroger springs with idle being more stable then your onto something and do more tuning of mech adv and timing to complete dialing it all in.

If it still idles poor after adv the base timing and ensuring the springs in the dist are ok then maybe you picked up some dirt in the idle circut or maybe if its getting considerably colder in your area you need to fatten/richen up the ilde mixture a bit or there's a vacuum leak.

Scott

Stewart, The first conclusion I had was also vac modulator on trans -- given that you have both a "dies at idle" problem and a trans shifting problem. The statement "Assume good for purposes of the post" is not the correct diagnosis.

You need to go back a check the vac modulator and you otehr vac hoses. For the vac modulator, use a MitVac to "suck on" the modulator (engine off) and see if it will hold vacuum. You can do the same with vac advance can on the distributor this way, and any other switches or devices. Use the spray can technique on all hoses. Do all of this first, in complete and exacting detail.

Next is timing.

Last is carb adjustment.

A quick/easy check on the EGR valve, with engine running, is to actuate it with the engine running by squeezing it through the cage and observing if the engine operation changes. Of course, you have already manually tested it with the MityVac as part of step one, so you will have verified that it doesn't have a vacuum leak and does indeed move when vacuum is applied.

I don't know whats in your carb, but I had a stock 66 vette 427 425 horse, and it would stall at idle, it had one of those black styrofoam looking floats in it, and it would sink.

Took it out a put it in a vise and you could squeeze the gas out of it.

OK, i got a vacuum pump and did all the tests and, also, replaced the distributor with another one i had. No improvement.

Therefore it must be fuel. So, i've decided to rebuild the carb (which probably needs to be rebuilt regardless).

My questions at this point are:

1) Regarding the accelerator pump lever and the two holes that the linkage rod that connects it and the throttle lever; i've read that all high performance applications---gto, corvette etc., always use you hole closer to the pivot. i would think that the hole furthest away from the pivot would provide more leverage and thus more "squirt?"

2) Does anyone off hand know what size torx bolts for the ones that fasten the top to the main body? For that matter what size torx bolts that fasten the vaccum break canister and idle stop solenoid?

http://i223.photobucket.com/albums/dd31/sencraig/100_0426-1.jpg

Stewart, the accelerator pump hole location is a "speed of delivery" thing, not a "volume" thing.

Sorry, can't help with the Torx question. But they are common sizes. If you have a typical 6 piece Torx screwdriver set, you will be covered.

Hi. I agree with the guy that thinks it's the carb. Sounds like it's flooding on you. The torx is a 25 if I remember right. The float is taking on gas or the needle is not sealing properly.

What if anything was done/changed about the time the problem started?
Does the exhaust smell rich, or is there black smoke?
Does it sneeze from the carb (lean)? Vacuum leak if so.

Nothing changed when the problem started *. i was just driving along and when i went take an exit ramp, the engine started to stumble and i noticed the vaccum gauge all eratic making broad sweeps across the gauge. In fact, that morning it started up just fine and idled just fine.

(*except it took longer to upshift than usual) i don't think it's the vacuum modulator on the trans because:
a) i replaced it 2 yrs ago, and when it went bad back then, the idle was not affected.

b) i did a vacuum test on it and it holds vacuum.


No black smoke, sneezing etc. All vacuum hoses checked.

We will solve this problem. i'm leaning towards the pump.

Stewart,

Agree with our "a" and "b".

How is the rebuild of the Q-Jet going?

Get that done first. Don't become a "parts swapper until its fixed" guy. Stay on the course of getting this fixed on step at a time. You will get there.

I'm wondering if there's a piece of debris either in the float bowl, fuel pump or fuel filter?....here's my deduction:
IF there is a piece of debris that cannot get by the jet in the carb, fuel pump or filter, it will settle once fuel pressure has dropped due to the engine dying. Once it has settled, the car will start because the immediate rush of fuel has not affected the debris....then once fuel pressure has pushed the debris back in the path of the fuel against a screen or passage, it will restrict the flow and cause the oscillation you are talking about. I know plumbers talk about this all the time with old pipes in buildings, to make sure any possible blockage debris is pushed out with a full rush of water, not just a stream. No matter the timing or vaccuum, if you're not getting fuel it won't run right.

There was alot of debris in the carb:

http://i223.photobucket.com/albums/dd31/sencraig/f9a6b450.jpg

Lots of orangish clay/sediment---i scraped away a little with a screwdriver just so we could get an idea of what i'm talking about. Lots of loose flakes (presumably from the "clay") There was also pet/human hair in there which i have no idea how it got in there. But the carb cleaner took care of all that. i ran carb cleaner thru all the idle passageways, then compressed air, then a wire.

i got the carb together yesterday. i don't understand why alot of people fuss over the Q-jet. It wasn't that hard. The most time consuming part (besides buying the new tools, reading, and waiting for the parts to come in) was waiting for the carb cleaner to dry.

So hopefully, this solves the problem. If not, it's probably the pump. i'm running out of things it could possibly be.

Dont forget to epoxy the sec and prim well/casting plugs on the bottom side of the main carb body prior to reassembly.

While your at it install a new float in you haven't already done so.

BTW,that carb wasn't that dirty,many carbs i pull appart for rbld are considerably worse then what your q-jet looked like.

Scott

i think i've pinpointed the problem----there is serious flooding going on; The new airhorn-to-main bowl gasket was drenched with gasoline, there were puddles of gas on the intake manifold and there was gas on the flare nut(i didn't tighten it enough). Also, before the carb was rebuilt and this overall problem started happening i subconscienciously noticed these puddles but thought that they were coolant, possibly due to not having enough lighting, also the air cleaner was probably blocking my view. Thus, i didn't consider it a problem.

The reason why i was able to tell now is i know what a new gasket should look like and could tell right off the bat that gas was getting on it whereas the old one was probably pretty drenched to the point where it changed colors. i know that the fuel level in a quadrajet bowl should be at most 3/4 full and definitely not higher than the bowl top.

During the carb rebuild, i put in a new float and checked the level to be good. i also vacuum tested the new needle+seat and put in a new filter. i also checked the old needle+seat, float and those were found to be good and at the right levels.

So, assuming the carb itself is not the problem, what else could cause flooding? Is it possible for a pump to go bad to be putting out too much pressure? The other possibility is there could be trash in the fuel system, but i don't think this is likely as when i rebuilt the carb, it wasn't that bad.

NOTEs:
a) i have a vapor return line on the pump.

b) the service manual says there should be 5-9 lbs. (will provide more detail later, don't have the service manual in front of me---i'm at work) This sounds like too much?

i wasn't able to test the pump pressure last night, will probably be able to get to it tonight.

* When you set the float lvl did you follow the inst where they state to measure the float lvl a certain amount of distance from the end/toe of the float ?

Not doing that will get you the wrong float lvl which could end up to high & flood.

* Are you setting float lvl with proper gauge to approx 1/4"-5/16" which is a good general float lvl setting for a q-jet?

* Also,did also make sure you used just the right amount of pressure(not too much not too little) directly on the float arm over top of the needle & seat to gently/properly seat the needle in the seat when setting the float lvl?

Not doing this correctly will also get you an incorrect float lvl adj that could end up too high & flood too.

* I have had people bring me flooding carbs they just rblt swearing they had the needle installed properly in the seat. well then wehen i would diaasemble the carb i would find the needle upside down in the seat so it could not seat /seal at all letting fuel come in under spressure all the time resulting in big time flooding.

* Are you sure the new float was not a new defective part or returned part taking on or soaking up fuel & sinking to bottom of float bowl?

Try submerging the float in fuel in an old coffee can for a few mins and then letting it go to see if it will float to the top of the fuel or if it stays submerged showing its bad/defective taking on fuel?

If so replace it.

The above mentioned items the 1st things i would re-check out when you have a flooding q-jet,dont just assume since you just checked the flaot vlv etc that everything is ok,people make mistakes with this kind of stuff esp when you not used to doing it every day and may have not been carfull enough when setting the float lvl esp when it comes to using just the right amount of pressure to seat the needle when doing the flaot adj and also taking the flao adj meas reading in the proper spot a little ways back in from the end /heal of the float like the inst state to do. Not getting 1 or both of those things right when setting the float lvl will bite you every time so check everything i suggetsed out 1 more time as i stated to do because they are the main things that can cause flooding other then maybe hoving over 10 psi fuel pressure. They state 6-7 psi max for best q-jet operation but i have also been ok in some applications where the motor run cool etc with as much as 9 psi so if you have an 8-9 psi pump i would no think if would push a new needle and seat to not seal prperly right off the bat,maybe later on a hot day of when it get worn a bit but not when brand new 1st shot on the motor.

And btw its not that uncommon for the airhorn gasket to get some fuel on it . But its not common or good at all to get enough flooding to form puddles on the intake,one pop/backfuire back thru the carb with that situation and you can have a nice fire on your hands so be carfull.

Scott

1) yes, i measured from the toe, used the right pressure, and gauge etc.

2) it's true, i can't positively say that the new float is 100%, but before the carb was rebuilt, the exact same thing was happening---i just didn't notice it. So, that's why i'm suspecting the pump now.

See if you can figure this one out:

The engine stalls out under 900ish rpm.

1) It's basically a stock crate 350 with quadrajet and stock HEI.

2) i've got EGR and a whole mess of vacuum hoses and whatnot (i will try to get a picture up ASAP).

3) i replaced the vacuum advance canister, but no improvement.

4) the engine starts easy, and after it stalls, it is easy to start.

5) the engine runs ok at rpm's above 1200ish. Maybe slightly rougher than normal, but basically ok.
a) the trans, however, seems to take alot longer to upshift than before.

6) it does not matter if in gear or not, and it makes no difference wether i'm coming to a stop sign or not----in other words, this happens in neutral regardless if the car is moving or not.

7) This condition just started about 5 days ago. It ran basically ok before that; It would idle in gear at 500rpm.
Sorry my first day here not sure if im doing this right but 1 to me sounds like vac. line in wrong place or 2 leak somewhere with vac. line. Glen

Please scratch the previous post---i found the flooding over the intake problem---the inlet nut to carb was not tightened enough. i was able to tell because i got my fuel pressure gauge hooked up and of course in order to see it, i had to start the engine and rush over to the front. And i'm glad i did because it was gushing out.



So anyways, fuel pump pressure good---the service manual called for 5.5-7lbs. and it was within those limits.

No improvement in the situation.

i don't think the carb is flooding at this point, but i'm not ruling it completely out. i guess the next thing to do is to measure the float while the engine is running. i know you need a special tool for that.

i'm leaning towards sticky lifter or valve, but i have my doubts about that as well; Let's say a sticky valve or lifter was causing the engine to run crappy at idle. Wouldn't this also cause the engine to run crappy at higher rpm as well?

i will try to get a video up on how the vacuum gauge is acting, which is very erratically at idle.

FYI,you cant meas float lvl with motor running with a q-jet,you were supposed to do it like i explained/sugested while the carb was appart when you were cleaning/rebuilding it.

scott

Yeah, i did it that way, i was just thinking this would be another way to verify float level which i really think is probably ok.

Anyways, i would like to thank everyone profusely for all the help. At this point i think i'm going to go back and check everything anally and the right way starting from the ignition.

Well, actually, before that, i'll put up a video on how the vacuum gauge is acting.

Try plugging off the vacuum modulator feed at the manifold to see if it improves your idle. The metal line running to the tranny may have developed a leak, uncommon but not unheard of. Power brakes? Check for a ruptured booster diaphragm. I had that happen on a 69 Camaro and caused the same problem you describe. REPLACE the PCV hose, it can get spongy soft and lose vacuum without having an obvious hole, ask me how I know. Still sounds like a vacuum leak to me.

You could be right; i'll definitely check those things. i think the only thing that needs to be connected to the carb to run (not driving) is the vac advance cannister and pcv?