My 86 Carb'd Iroc with 305 (Stock), has started running like crap when you first start it. REALLY hard to keep it running, in December I had replaced the old Q-jet with a rebuilt one so I didn't think it was the carb, but it really sounded like the choke was not working right. I was fooling around under the hood and removed an electrical connector on the front of the carb and it runs GREAT now.
I think the sensor is called a TPS. when I connect it I hear the constant clicking noise it makes but when disconnected it goes away and the car idles nice and smooth. I tried starting it this morning from a cold start and it fired right up nicely. What is wrong - a bad TPS or something. I have ordered a new intake, carb and dist so it really doesn't matter but I would like to know so when I sell it I can accuratley inform the buyer. Thanks
Tony

 

That is the mixture control solenoid. May be out of adjustment if it runs like crap. It should be clicking, that means it's working.

 

You've also got a vacuum port "open" in that picture, perhaps only after you pulled the air cleaner?

With the plug pulled, the carb should run "full rich" on the primaries.

IIRC, the MCS should click with the key in run, engine off.

 

The vacuum line open on the front is the one to the air cleaner. I have a clicking sound when the ignition is in run coming from the MCS. It is a bitty to keep running when it is hooked up. I was monkying around and disconnected it and it idles much better from a cold. with it connected it is like it is not letting the choke operate properly. When I disconnect it the choke seems to work just fine.

 

i see 2 things that doesn't look right, it looks like the lock plug for the lean stop adjustment is missing, from the normal action of the MC solenoid, the lean stop adjustment screw can turn in causing it to bottom out & run lean, or turn out & cause it to run rich.

the lean stop is #1. it can be set pretty close without pulling the carb apart. with the right tool, turn the lean stop screw down all the way, do not force it, the threads are very fine & they will strip out easily, once it is seated all the way down, turn it back out 2 & 3/4 turns, this is close to where it needs to be.

its hard to tell from the pic, but it also looks like the lock plug for the rich stop is missing too, the rich stop is # 2. it is adjusted with the carb almost fully assembled, after the lean stop is set, a special measuring tool is inserted into the hole marked #4 & pressed down, read where it is at, then with it released, read where it is at, 4/32 is the right adjustment for it. the same tool for turning the lean stop is used for the rich stop.

the last adjustment is #3, it is the idle air adjustment, it's height is also set with a special measurement tool.
depending on which the idle air valve the carb has, it can be used to make a fine adjustment to the idle mixture.

 

I will check this out tonight to see if I am missing screws in that puppy or not. I will post more in a bit. thanks
Tony

 

It's obviously been messed with, the riveted on "cover" for #3 is missing. Good catches.

 

This was a rebuild I bought from carb exchange last dec.