hesitation off idle problem?

[benoit454]

Hey guys,

I got a question for all of you.

Recently we purchased an 84 c10 swb truck, it has the 305 h.o. with a 4 bbl quadrajet on it, th350 or 350c trans and 2.73 rear end.

It's all stock as far as we know.

When we first got it the choke was sticking(electric choke) and idle real high because of it, like having cruise control while driving. Well it also dieseled bad too, so we wired the choke open so it wouldn't do it anymore.

Then we put in a new set of plugs.

Ran ok, but had problem warming up, I know I know, with no choke it will, so I overlooked it. Then last friday it wouldn't hardly run at all, and I let it warm up for like 5-10 minutes before even trying to put it in gear. As soon as you give it gas, falls on it's face, trys to die, runs very rough, doesn't really cough or anything. Just doesn't want to run, after it's warmed up, it's better, still has a bad hesitation, like a stumble off idle though, but just for a second.

So I put on some new accel wires I had on my car, and I know they are perfect, then last friday put on a brass terminal cap and rotor. The old rotor was black in the center lol.

Well we also adjusted the choke on it and let it work as it should. Well choke doesn't work anymore, doesn't choke at all. Ran ok, but still hesitation, and today it acted up badly again. When it acts up, you can't hardly pull out, you can floor it and it just bog down and go nowhere fast. Then after a few seconds of trying to floor it, it'll stop stumbling and go on somewhat, or if you are lucky the passing gear kicks in or four bbl one, and it goes on.

I changed the feul filter today, inside the carb and still same thing.


Anyone have any idea on what to check, change, or fix?

it's got about 97,000 original miles on the truck.

I've already put in ac delco plugs, accel wires, duralast brass terminal cap, and rotor button. Then put in a new fuel filter today, and still right off idle, it stumbles and hesitates. You don't even have to be in gear, you can be in park and hold it down just a bit and it stumble and miss and crap it seems like badly.

When it's warmed up and driving though it's damn near perfect, great power, pickup and take off, just a tad bit off roughness right off idle but only for a second then it's fine.

But when it's cold like just starting out in the morning, it's bad. Thing is after the new cap and button, it seemed better, didn't do it as bad as last friday, until today, it acted up just as bad today as last friday.

[benoit454]

Ok this thing is really ticking me off, started it up after the new fuel filter, seemed ok at first. Had the bad spot right off idle where it ran rough again, setting in the carport running, behind it would burn your eyes out, seemed rich.

Well going down the road today it was stumbling, rough running as hell, tried to die out, did once, sputtering or whatever, coughed once, and kept surging, under steady pedal, same distance down, just started surging. Never stopped. When it stalled it smelt very lean or something, had a funny smell behind the cab and around it. Wasn't fuel smell really, my old man said smelled like it was running way lean, and starving.

So as soon as it cools off, I am going to pull a few plugs, and inspect them.
Probably change fuel pump, since it's probably 1984 I figue it might be acting up or bad. if that don't work I guess the carb is gona come off, so we can get to the mixture screws, drill out the rivets and adjust the choke(which is wired open now) and try that.


Anyone else have any ideas?

It wouldn't NOT have enough backpressure to run good should it? with this setup....

factory manifolds, y pipe, 2-1/2 pipe, flowmaster 40 single 3 inch in, dual 2-1/2 outs, and no cat.

[benoit454]

Ok my old man was right,

It's running very VERY LEAN!!!!!!

The plugs have been in it for like 2 weeks and they looked as if NONE of them had been firing, they were bright white, and the tips or the arm over the electrode the paint was worn off it like it was bare metal/silver appearance.

I already replaced the fuel pump, and made sure my filter was in correctly lol. So I need to either try it out now, or take the carb off so I can gain access to the mixture screws, and then adjust them.

[OlChev67]

Yeah, sounds like a carb thing to me. Any vacuum leaks? Hope you figure it out.

[benoit454]

Well guys it was definately carb issues.

After putting the pump on I tried it out, left fine, but I didn't make it a 1/4 mile up the road and it started acting up badly. I limped it home, jerked the carb off of it, knocked the mixture screw caps off, adjusted the mixtures screws out about 3-1/4 turns.

Threw it back on, runs freakin GREAT!!!!!!!!

it had this miss in it before, ever since we got it, like the motor would hit a hard spot, GONE!!!, hesitation, GONE, sputtering, missing, dying, bog down, all gone.

She's good now. I still need to find a tol that can adjust the screws while it's running, and hook up my vaccum guage or tach/dwell meter to it. That way I can set the mixture screws right.



Here's another question though, anyone know exactly how when the e.f.e. opens/shuts? The one in the passenger exhaust pipe manifold, it's vaccum line is in the air cleaner lid, and I have no idea how it can get vacuum to open up and work. I checked it and it wasn't opening up, found a capped vac. line, plugged it in, and it opens up now. I put it back to normal though, if it works ok I'll leave it alone, if not I'm going to hook it back to the capped off t so it will open up.

[lurch115]

if i remember right on that e.f.e....if it doesn't have vac. pressure to it...it should be open.... if you hook a constant vac. to it you'll know if its pulling that flap closed cause that exhaust manifold will get really hot, and your motor will run doggy after it is warmed up

[benoit454]

Thanks for the info.

I left it alone like it was so it should be good. We weren't sure on them since it had been a long time since we messed with one. Couldn't remember if vaccum opened it or shut it. it probably does shut it, because on constant vac. on a test drive it sounded funny on that side, like exhaust leak or something.