My Pinto seems to be running too rich and I have the black smoke, crusty plugs, and a second opinion to almost confirm this. What could be out of whack with the carburetor or smog control to cause this and how do I fix it? It's a '79 2.3 with an automatic.

This could explain a couple of bonehead repairs by the previous owners to fix this. One was removing the choke butterflies (which I still haven't replaced). The other is pulling the wire out of the idle dash-pot.

Thanks for the info!

BTW, would a '78 carb interchange with a '79. I got one on my '78 parts car.

Does your car have the feedback carb with an oxygen sensor on the exhaust manifold and an electronic module under the dash?

Does your car have the feedback carb with an oxygen sensor on the exhaust manifold and an electronic module under the dash?

Wow, haven't seen a O2 sensor on a Pinto yet. Not saying they didn't, just never seen one.

Uhhh, you may have the cart before the horse on this one.

From '75/76 on, the car should have a catalytic convertor, and an air pump, possibly also has an 02 sensor and a feedback carburetor too. If any of these is acting up, disabled, not working at all or missing, that could be the source of some of your symptoms.  It's worth checking before looking elsewhere, especially if an engine/car has over 100,000 miles, or on ANYTHING this old.  Convertors can get plugged up with cars just having been sitting around too long also, and electrical wiring acts up more with accumulating age.

Check the easier stuff first. 

Pull the 02 sensor and check it out. Then check the air pump.   

If yours DOES have an oxygen sensor (I don't remember if the '79 did, but I suspect that it does), and the 02 sensor isn't working properly, the engine management system is typically supposed to make an engine go to a richer mixture mode when this happens as a failsafe, so that the engine doesn't run too hot. The reasoning goes that even if the engine is then running rich, it will take longer for THAT condition to cause long term damage than if it runs too lean, which can cause damage in a hurry. And maybe someone will notice what is happening and fix it before it's too late.

 For example, let's say that the 02 sensor is plugged up with carbon or the sensor wire isn't making good electrical contact.  Then the engine shifts to a richer running mode. If that is what happened, you may have noticed a decrease in fuel mileage from that point, and that's usually what people notice first, even before any performance issues.

Or, if it doesn't have properly working catalytic convertor and/or air pump and is just burning oil for example, it would tend to be running rich and the 02 sensor should be able to pick that condition up and try to correct for it. This MAY make an engine knock more evident under load, as the fuel mixture would be being leaned down to compensate for the burned oil passing through the sensor. While engine oil can be considered fuel, it doesn't burn at the same speed as gasoline, so some of it gets through the combustion chamber as unburned/partially burned and can form deposits on the plugs, 02 sensor, cat convertor, etc.

The "crusty" plugs, unless they are actually very sooty and/or oily down to the metal shell, may actually just be a "normal" accumulation of crud (from high mileage and them having not been changed or cleaned in too long a period of time), which is then being overlaid by something that started more recently. Like maybe from a bad set of plug wires or a cap/rotor problem, a weak coil, etc. causing a frequent miss.

The reason that I said a properly working convertor, is that any halfway working convertor will clean up the exhaust to the point that it would be difficult to impossible to see any smoke from oil burning, unless it was burning through oil at something like 200 miles or less per quart, and I think that you would have noticed and mentioned that.

 My wife once had a 4 cylinder car with stuck oil control rings in 2 cylinders that was burning oil at the rate of 50 miles per quart and except on very fast take offs, (the car still RAN fine) there was NO evidence of smoke in the exhaust. There was a tiny bit of carbon in the tail pipe, but hardly noticible. Her plugs did load up quickly, but they were mostly wet carbon fouling.

Had another thought. Perhaps the previous owner had the carb apart and switched, knowingly or not, the primary and secondary jets. The secondary is bigger and would make it run rich.

If the car has a O2 sensor as has been suggested it would be in the exhaust manifold just before the down pipe. Should be able to see it fairly easy if it has one.

A feedback carb would have a couple wires going to it attached to a solenoid somewhere around the fuel bowl. Never seen one on a Pinto so can't tell ya exactly where. Just don't mistake it for the bowl vent that would be over in the corner of the top plate. There wold be a larger vacuum hose attached in the front of the bowl vent sol.

I think I'd just drop the other carb on it just to see how it runs.

Found that a lot of the bad MPG problem was caused by a cracked and leaking fuel return hose back at the gas tank. Replaced both hoses there.

So what is it about Pintos and gas tank issues? :evil:

Got the carb off the parts pinto and am soaking it and will rebuild it at leisure.

Is this the solenoid on the firewall? One of the lines is plugged. Plus the plugs that started this all. The fuse for the idiot lights and emission was blown and since replaced. The carb is soaking in the vat waiting for the parts to come in.

Is this the solenoid on the firewall? One of the lines is plugged. Plus the plugs that started this all. The fuse for the idiot lights and emission was blown and since replaced. The carb is soaking in the vat waiting for the parts to come in.

Does the car have a/c? that looks like the solenoid that increases the idle when the air conditionong is turned on.

Haven't checked in for a while.
Lugnut has some good things to say. I had forgotten that my '71 was itself originally a California then Arizona car, and in that era as now, Calif. cars would frequently have emission controlled engines with systems a year or 2 in advance of the 49 state models. Plus the Canadian cars are also frequently different.

You'd be well advised to check the VIN carefully and also find the state (or Province) of original registration of your car,  to at least have a better idea of what it started out having in the way of emission controls, so that IF you need parts, you will know what is supposed to be there and what isn't. And then getting a GOOD shop manual, (preferably the Ford factory manual), if you haven't already done so. They aren't all good. It helps to know the proper information as there may also be some minor changes elsewhere on the vehicle if it is a non-49 stater or a Canadian vehicle.

You asked "what is it about Pintos and gas tank issues?"

No USA car in that era was made with fuel lines  (or vacuum lines, coolant hoses, belts, tires, or basically any partly natural rubber part, and many of the more engineeered elastomeric compound rubber products too) that were INTENDED to last 20, or 30 years. (Many/most current cars still aren't.) All of the rubber lines in the entire car should have been replaced at least once by now, and probably many of them are still the original ones. 

Knowing this doesn't mean that you HAVE to run out and replace everything rubber right away, only that if you choose not to, that you shouldn't be surprised when this type of part eventually fails. (not if)

Out of self defense over the years, I've taken to replacing a lot of older engine and safety related parts such as v-belts, hoses, timing belts, brake lines, brake parts, shocks, tires, etc. as soon as I can get to them as part of a catch up/preventative maintenance program for any older or high mileage car that we own. I concentrate on the more critical rubber stuff and fluids as a first round go through.  Saves me a lot of time, money and hassle over the long haul by preventing breakdowns that could have been anticipated and by my not having to do or having someone else do parts replacement when the vehicle is AWAY from my garage.