can someone shed some light
when i start the car i have to keep my foot on the gas or it dies.
it first starts onall 8 then gets lumpy until its on what feels like 4.
i keep my foot on the gas and slowly it begins to smooth out until its on 8. loads of black smoke. the choke flap on top of the carb seems to work ok. and some times when its on 8 the fast idle dissides to work. if i have to start it more than 1 time without geting it up to temp.it wont start and all the plugs are black and i have to get them out and clean them. i do allso have 12 volts at the choke coil, any body any ideas

 

Sounds like the carb is running VERY RICH. Turn the idle mixture screws in untill some risistance is felt, then back them out 1 1/2 turns, then start the engine up, get it to operating temp, then mess around with the IMS's a bit, untill it runs the way you want it to.

 

Hold your horses,
The LAST thing you want to do is tweak something if it's NOT the problem.
I was not aware that the "IMSs"es had the ability to back themselves out of adjustment (both of them? Or just one?).

Sorry 6ROC,
I don’t mean to “flame” on you ( Welcome to the Board). I think it is COOL that you are willing to try and help someone out with their problem. I just happen to believe that “no advice” is better then “bad advice”. In the future, you might want to ask a question or two before jumping in.

It sounds to me like this guy is describing a “start-up/warm-up problem. I see no mention of an “at normal temp” problem. Like you imply in your reply, the IMSs have most effect at normal temp.

I have never experienced this problem myself, but let me do some research, then hopefully hand out some better advice. This sounds familiar.

 

iforgot to mension that at normal temp the plugs burn clean

 

i think i am having the same problem...my car seems to running really rich(black smoke, popping, etc.) at start up. Then after it warms up it's fine. the timing is ok, i've adjusted the IMS's, the idle control screw and it still runs rich at start up. i think it may even be slightly rich at operating temp.(i can smell gas most of the time). also still have a dieseling problem if the car gets hot.

 

Thats all right, I did jump in, as I forgot to even ask what kind of carb he's got . The reason I gave him this advice is because about a month ago I had the same exact problem. The advice I gave you is the way I fixed mine. I've got a non-cc carb, I have no idea what ian's got, so... what kind of carb do you have ian?

 

my carb is a cc 4 barrel rochester

 

Well then, ignore my suggestion then, I've got an edelbrock 600.

 

Hey Ian,
You say the choke flap appears to be working. Take a closer look.
With the air cleaner off and engine cold, tap the throttle to engage the choke.
The choke flap (snicker snicker) should be in the “closed” position, but it should be loose, able to move freely from fully closed, to slightly open.
The choke flap will be fully closed during cranking so that raw gas (petrol) can be “sucked” from the carb at very slow RPMs, but as soon as the engine starts and RPMs speed-up; a vacuum diaphragm (the choke pull-off dashpot) mounted on the side of the carb pulls the choke flap slightly open to feed some air to the motor. It sound like this is not happening for you.

 

dukemushroom1,
What type of carb do you have?

 

hey i gotta 84 L69 with a cc Q-jet 4 barrel and i have been plagued with the same problem as the other guys.....im away at college so i cant go out right away and try to try these suggestions so i hope one of you guys figure it out and can lead me in the right direction.....thanks

 

ok cheers
i will have look and get back asap

 

i have a holley 750cfm, 4bbl, vacuum secondaries, electric choke, it's basically the cheap version of the street avenger.

 

nice one
you got it spot on. i just give it a bit of help to open a little more and it smoothed up realy nice, and ran on its own.
the thing is now what do i do to correct the problem ?

 

so ian u are saying that you tried the choke flap thing and when u opened it a little bit it ran fine........so then all u would need is the little choke pull-off thingy....who sells those?

i hope that is the problem for mine...im goin home this weekend and will have to check it out and see...

 

Ian,
Does your carb have the vacuum dashpot (vacuum diaphragm)?
It serves two functions.
1. It “pulls-off” the Choke flap after engine start.
2. It closes the Secondary Air Valve (the SAV is the thing that looks like a choke flap for the secondaries) when the throttle is closed (Some people remove it because it can prevent the SAV from opening quickly at WOT, but then they end up with the starting problem you have).

NOTE: Some carbs have two dashpots, one for the SAV and one for the choke pull-off. They are also referred to as “vacuum break”s

I don’t have my car or spare carb handy so I am working from memory, I think the dashpot is mounted on the upper back of carb on the passenger side. The linkage shaft coming out of the dashpot goes forward to a half moon shaped slot on the end of the SAV shaft. This dashpot linkage also has a small plate with an adjustment screw, a second linkage comes from the small plate to the Choke flap, the adj screw is used to set the amount of choke pull-off when vacuum is applied to the dashpot. I’ve never had to adj this screw myself, seems like you could:

Start the car, hold the choke flap open with your finger, then adj the screw until the flap is being held open by the linkage.

MattW,
You could have a bad dashpot, plugged vacuum line going to the dashpot, bent linkage, or misadjusted pull-off screw.

 

i'll have to try...thanks for the advice...

 

ok mine has 1 vacuum pot on the pasenger side
i will have a look with the screw and see what gives
thought i would ask because i know some of them are done by bending rods. i didn't know witch was witch.
i will let you know how i go on

 

adjusted the screw and great, thanks again for the info
later dudes

 

This is my problem to the T... anyone have a picture or diagram I can see for this adjustment screw?

 

. forum didn't put this to the top on the last post...

 

its very rough but should do
i might have a good one if needed

 

does this help?

 

that picture is fantastic

 

if you also have a problem at WOT, your choke pull off may not be working correctly. Does it hold a vacuum? I have 2 rochester carbs. The 1 in my car wouldnt hold a vacuum and neither would the old parts 1 that came OUT of my car, so i bought a new 1 for 17.97 at autozone. I will install it tomorrot to see if it solves the problem.

 

i work at autozone so if thats the problem for me i get discount woohoo

i actually think that may be my problem because when i used to take it to the drag strip it would always bog down right around 50 or so at WOT ...i always had to let up and then floor it again....sound like it still? or do i have other concerns that i should deal with?

 

ok, take off the air cleaner. The easiest way to check is to take a look @ the choke pull off... (the thing with the screw weve all been talking about with a metal hook that connects to the secondary flaps). Start the car. Does the choke pull off "go down" and push the choke off? ... after the car warms up, manually hit the throttle (while still under the hood) and see if the choke pull off moves. Does it move a lot and or not return back to the "DOWN" position? If you answered no for question 1 and yes for question 2, youve got a problem with the choke pull off. It has a vacuum leak and does not hold the vacuum. Replace it and youll notice better performance and easier starts.

peace

tom