So I rebuild my carb. Its an MC2100 that uses the adaption plate for the PCV connection on the manifold.

I let it warm up and put the idle at 900. Then I did my best to set the mixture by having someone tell me when the RPMs dropped and such till it stopped smoking and such.

Idles pretty rough. So I rented a vacume gauge thing from Advanced to check it out. Not sure where to hook it up. I hooked it to where the distributor went to the carb, but it has no vac at all. Does it need it? Hell if I know.

On the back of the carb there is a place next to the PCV valve inlet, I put it there and it never goes over 5. When I start to play with the mixture, you can hear the PCV valve rattle like crazy.


Anything to look for or check? What am I doing wrong?

Runs good just shakes the whole jeep when it idles.

This will be like the blind leading the blind, I don't even know what kind of carb that is. If it was a Holley it would be a piece of cake...

What kind of carb is it? Motorcraft I assume.

My best advice is to adjust it so it idles clean and check the plugs and watch the tailpipe for puffs of black smoke or a rich smell. Basically richen it and work your way lean right to the point of not fouling plugs.

Maybe there are other problems? The float set to high? On a Holley if the power valve leaks, that makes it idle rich.

This will be like the blind leading the blind, I don't even know what kind of carb that is.

umm....


Its an MC2100 that uses the adaption plate for the PCV connection on the manifold.


Not really sure what you are talking about with all the pulling the plugs and such to check the mixture, but I do need to pull them anyways to see whats up. As of right now it dosn't smoke at all. Maybe its rare, but I have an AMC motor that dont blow smoke.

With the engine off, turn the idle mixture screws in until they lightly bottom out (don't tighten them down), then back them out 2 turns. Hook the vacuum gauge to manifold vacuum (not the dist. port, it only has vac when the throttle is cracked). Start the engine and adjust the mixture screws evenly (both the same amount) until you get the highest vacuum reading. Your idle speed will change depending on the mixture screw settings, so you will have to keep adjusting it to keep it idling where you want. You want the highest vacuum reading you can get, at the speed you want it to idle at. This whole process should take less than 10 minutes.
Travis..

With the engine off, turn the idle mixture screws in until they lightly bottom out (don't tighten them down), then back them out 2 turns. Hook the vacuum gauge to manifold vacuum (not the dist. port, it only has vac when the throttle is cracked). Start the engine and adjust the mixture screws evenly (both the same amount) until you get the highest vacuum reading. Your idle speed will change depending on the mixture screw settings, so you will have to keep adjusting it to keep it idling where you want. You want the highest vacuum reading you can get, at the speed you want it to idle at. This whole process should take less than 10 minutes.
Travis..That's kind of the baseline "by the book" way, you want it adjusted on the rich side of the highest vacuum reading. If it's a smog carb the mixture screws may not even do anything, or very little.

If you can't make it run good the way I listed, there is something else wrong. Yes, you can adjust them OUT until the vacuum reading starts to drop off again, and that will be on the rich side.
Travis..

Yup, thats what I did, but I couldn't get it any higher than what I did playing it by ear and such. So I took it back. Runs good.

It does hwoever run a little icky int he morning, its still kind of warm at night here so I'm thinking its just the choke setting. I'll pull the plugs and see if I fouled them up trying to set it and clean them up/replace.

I'll take that back, it runs damn good. I want to buy a manual cable choke.

But I don't even know what the choke is for or how it functions. I just know for some reason when you first start it cold it has to be closed for some reason.

A choke restricts the amount of air the engine can take in, thus creating a rich condition without having to have any change in the fuel circuit. A cold engine doesn't like to run on a lean mixture like it will when it's warmed up. As the engine warms up, you need to open the choke more and more depending on how it runs until it's fully warmed up and can run good with the choke full open.
Travis..