Low throttle bog

[recian]

First off, engine: 305 auto 2wd 2bbl rochester carb
So now that my vacuum leaks are fixed I noticed my truck runs alot better. However when it's cold at low throttle like barely off idle lightly accelerating the truck bogs like something is holding the engine back. It'll run good at med throttle. Is this just a characteristic of the carb running rich in choke? I work a mile from the house so for now when I go to work the choke never turns off.
This problem seems to go away when warm even tho the choke is broken and never turns off. I have noticed the truck is hard to start like it's flooded and if I gas it while cranking it'll blow black smoke. The truck used to diesel for a couple seconds after shut off but that problem seems to have cleared up.
I'm wondering if it's just time to find a quadrajet and rebuild it.

 

[MrMarty51]

Choke pull off, sounds like it needs adjusting. Unless, the choke is not fully closing.
Q-Jet`s a good choice, with the Q-Jet manifold.

 

[recian]

I'm thinking it could have something to do with the vacuum advance. It's run off a thermo switch that allows vacuum only when warm. There's 2 of them on the truck that control the EGR, vacuum advance and evap canister. I know what's wrong with my choke. It's electric and the rivet on the cover broke so the spring inside is hanging out. I've considered just going to a 4bbl so I can get that 2bbl drivability and the extra 2 will open at certain vacuum or throttle when I get on it or am hauling a load. Yeah I want to stay with stock quadrajet mainly since junkyard is a good place to find cheap parts. I've considered going with something like this: It says fits 350 so it should fit the 305

http://www.ebay.com/itm/Edelbrock-P...Parts_Accessories&hash=item4d0f71de12&vxp=mtr

 

[89Suburban]

Many good points, also the EGR valve is notorious for that symptom.


Posted from hell

 

[recian]

So the intake could take care of it since it'll elimiante EGR and EVAP which I've wanted to do. I want the alum. intake and a better carb but keep the stock look

 

[Jims86]

So the intake could take care of it since it'll elimiante EGR and EVAP which I've wanted to do. I want the alum. intake and a better carb but keep the stock look

Check your distributor for proper function befor spending any money, otherwise, you will have a new intake and carb, and still have the problem as well. I always say, baseline stock before mods... that way, you can really enjoy the results.

 

[recian]

Yeah you're right. It probably could use a tune up anyway. I know the whole ign system has over 60k on it. I'll pull the cap and check the rotor button. Does it use points? Using a simple vacuum hand pump i can check to see if the advance is working right?

 

[Jims86]

Yeah you're right. It probably could use a tune up anyway. I know the whole ign system has over 60k on it. I'll pull the cap and check the rotor button. Does it use points? Using a simple vacuum hand pump i can check to see if the advance is working right?

No, its electrinic. make sure the weights under the rotor move freely....maybe clean them up a bit.

 

[recian]

Got it. I'll check that tomorrow. But what about the vacuum advance? No way to check that?

 

[Jims86]

Got it. I'll check that tomorrow. But what about the vacuum advance? No way to check that?

put the vac line in your mouth, and suck on it, if it holds, its good....less you have a vac accumalator.

 

[recian]

Idk. This is my first carb'd old school truck. I come from EFI and advanced OBD computer cars. I know how it works but as far as the nitty gritty, this stuff is unfamiliar to me. I know there's a bubble looking accumulator on the distributor with a vacuum line on it lol

 

[Jims86]

Idk. This is my first carb'd old school truck. I come from EFI and advanced OBD computer cars. I know how it works but as far as the nitty gritty, this stuff is unfamiliar to me. I know there's a bubble looking accumulator on the distributor with a vacuum line on it lol

That would be the advance servo...usually hooked to a ported vac source on the carburetor.

 

[recian]

89Suburban could you elaborate on the EGR or how to test or eliminate? I replaced my spark plugs, wires cap button etc and it runs a hell of alot better and it's not nearly as bad off idle but that bog is still there like something is holding the engine back. It's not nearly as bad and the engine no longer rumbles at idle, it's smooth. I'm surprised that truck was even running as bad as that rotor button was. I checked the advance and it works freely and the points dont seem to be corroded at all. Unfortunately I didn't have a set of brass gauges to check them while it was apart.

 

[recian]

Ok now I feel kinda stupid. I turned the a/c off and boom it runs perfect. Yeah there's a very slight lag in that spot now but you wouldn't notice it otherwise. My old ram truck you could turn the a/c on and the engine didn't even know the compressor was on and it even had an air pump being run by the crank too. Didn't think v8s lagged that bad when the compressors were on.

 

[recian]

89suburban, could you explain the EGR? I went ahead and rebuilt the carb I have since kits aren't so expensive. It ran way better at first and the choke is doing what it should but it's fell back into it's old habits. I'm wondering about EGR now. It makes sense. EGR tends to be used on light throttle which means off idle to about 50% throttle. It's like when you hit 50% there's a turbo that kicks in and it takes off.