Running rich?

I have a 1990 Mazda b2200, carbed, automatic... With 150,000 kilometres on it.

It was running fine, and now has aquired some issues. Looking for some help/direction, and can't afford a Weber. So trying to diagnose the stock carb.

Here's the symptoms:

- starts and runs fine with choke on, but dies when put into gear. Once warmed up partially, it runs quite smooth and normal. As soon as its warmed up fully, it starts to run rich (sputtering, fuel smell, rough idle). But on the highway, seems to be fine.

-Checked the plugs, they show that it's running lean.

-Trucks getting decent mileage (22 mpg).

- in the vacuum lines, there was some fuel... Not sure how it got in there.

Wondering if this could be a mixture solenoid issue? An ecu issue? Or possibly a carb float issue?

Any thoughts would be greatly appreciated... Looking to take this truck on a long trip soon... And would like to have this figured out.

Thanks.

Upon doing some more research... I'm convinced it's the mixture solenoid... What's the best way to remove the top of the carb? Do I need to clamp any fuel lines? Anyone have a write up?

Thanks.

When the mixture control solenoid quits working the carb defaults to a really rich condition and gas mileage drops to about 20 mpg. The fact that you are getting 22 mpg and the plugs showing a lean condition means that the solenoid is probably doing its job. But to answer your question, there are seven screws holding the air horn in place and there is a small o-ring sealing the solenoid so you have to lift the air horn after you have removed the screws by prying up gently between it and the carb base. I'd look for a vacuum leak or a plugged idle jet.

Thanks for the reply.

So I don't have to worry about disconnecting any linkages, or plugging any fuel lines?

Just remove the screws on top and pull the air horn off?

Do you still have the giant bundle of emissions related vacuum lines attached to it? Here's what I did:
Truck was running like garbage. Poor mileage, backfiring, sputtering, etc. Order a rebuild kit from local parts store ($50 or so). I took out every conceivable vacuum line I could, and removed any and all emissions junk from the fender well. Removed carb, and remove air horn. Blow clean compressed air through any orifice I could find, and installed rebuild kit.
The part that puzzles me is that the carb has fuel cut off solenoid, idle mixture solenoids, and all sorts of electric wizardry on it.
Plug none of it in. None. Leave them all unplugged. Truck runs like a champ. Solid 25mpg city mileage. Dependable, always starts. I live in manitoba, and -25C to -35C is not uncommon in winter. No problem for the mighty mazda.

Really!

Yes it does have all of the stock emissions and "electronic wizardry" connected.

Would it be possible to just unplug the ecu and achieve the same results?

Thanks for the reply

I would leave it plugged in. I'm not sure if my method is right or wrong, I'm sure that there's some guys here that would swear at me and call me stupid for disconnecting everything, but it sure seemed to work out in my case.
Unplugging the Ecu (brain box?) Wouldn't do any good I don't think. Are you talking about the box in the left front corner by the headlight?