I would double check the tps and clean the tb.

 

Also forgot to mention I replaced the fuel pump and fuel filter before I adjusted the tps sensor because my car was weak under 2k rpm so you might want to check your fuel pressure

 

Thanks for those ideas. I'm out for travel again and won't get to the car for a while but will dig back into this (or find a gy who can do some work on it for me) pretty soon. We shall see...

 

Yep

 

Update on this. Car has been in the shop, techs there say the ignition is good, spark is not the problem. Have isolated it to some component in the vacuum system, am trying to get more specifics but when manipulating parts of the vacuum system (under the air cleaner) by capping off different hoses, the problem goes away and the car runs smoothly. Am hoping to get pictures and more specifics from the tech.

 

Another update, seems to be something with the vacuum system, attaching some pics and here's what I got back from the mechanic:

"This is the suspect problem, when plugging the large hose to the air cleaner, it idles, and runs properly."

Not sure if that helps any of the experts on here. I have been traveling a lot, car has been in the shop for weeks, they are getting to it very piecemeal, which is fine, I'm in no hurry. But with me being gone and them not giving the best guidance on their troubleshooting efforts I'm fumbling in the dark here a bit.

Any ideas? Thanks all.






This is the part they think may be the problem.

 

That blue vacuum valve isn't factory.

 

More photos and diagnosis, from the mechanic helping me out:

"red rod is pointing to where I get vacuum leak if not plugged, I think it is supposed to open above a certain rpm, but is always open"

 

Culprit seems to be the malfunctioning of the Air Control Valve, and of course I cannot find a replacement anywhere in my basic Google search for parts.

"When I apply vacuum here it does not hold any vacuum, makes me think the diaphragm is bad"

 

Like its name suggests, the function of the ACV is to divert or control air coming from the air pump for emission purposes. It contains 3 valves, two of which channel the air (called secondary air) to the heat exchanger in the exhaust system. This pre-heats the air before it is sent back to the thermal reactor. (the part that is bolted to the side of the engine)

This secondary air flow controls the temperature inside the thermal reactor so that it can more effectively burn up the hydro carbons contained in the exhaust gasses. In short, helps to reduce the un spent exhaust emissions. The third valve (the diaphragm you are questioning) is the anti-afterburn valve. It is triggered by the solenoid off the side of the carburetor with the yellow dot on it and allows additional air into the intake manifold during deceleration and engine shutoff to help prevent afterburn or backfiring.

I don't see why this valve would affect your idle or cause a power loss as you first described your problem. Here are some pages from the 79/80 factory technical information manual that explain the valves function in greater detail. It also has some checks for the valve, but you need to know if your car was a California emissions vehicle (sold new in CA) of a "Federal" (49 state sold new) car to properly test the No 2 relief valve.




No 2 relief valve test-California emissions car:


No 2 relief valve test-Federal emissions car:

No 3, Anti-afterburn valve-deceleration control:


If you want to try another ACV you can PM me as I have a few SA specific spares, but I don't think its really your problem. If a diaphragm is bad, or you have a vacuum leak, it will always be bad and not sometimes work and sometimes not. I still think that my first suggestion on page one about the clogged pickup tube in the tank could be possible or some other fuel or carburetor related problem.

 

Mechanic thinks he's found the problem, bad ACV solenoid. Has tested this one in the photo, it's not functioning:





Trying to find a replacement...

 

@Banzai Thanks very much, great info - will pass this along.

 

Before you do that be advised that yours is missing a cap on the nipple opposite of the electrical connection. Here is one I just removed from an 80 carb that is going on a spare engine I had rebuilt.




You can first try capping off that end. If that has no effect, you can also take it apart first to see if you can free it up. One of the nice things about these cars is that they are so analog, from a time when you could actually fix things instead of just being a professional parts changer.

Might be giving away a restoration secret or two, but theses solenoids aren't too complicated. Normally, they fail just by getting all gummed up and corroded inside to where they freeze up. Some careful disassembly, scotch bright and WD-40 might bring it back. I did this one in about 15 minutes just to illustrate.

First, take a couple pictures so that you know what it looks like all assembled. Straighten out the 4 small tabs at the one end and don't forget the single tab that crimps around the small pin on the one side. Tiny screwdrivers followed by slightly bigger ones work well here.




Next, pry and carefully pull it apart. Be patient and work carefully as the plastic nipples on the valve body can be old and very brittle.



You will end up with these 4 pieces.



From here, just remove the center brass plunger. It will have what looks like float bowl needle and small spring at the other end. Get some WD-40 and some fine scotch bright and clean up any residue or corrosion.



To re assemble, just reverse the steps. I've used this method to resurrect entire emission racks to good effect.



Could be wrong, but If you get it operating again, I still think you are fixing something that doesn't solve your problem.

 

@Banzai Can't thank you enough for this detailed explanation. Very helpful, have passed it on verbatim to the guy working on the car. Will see if this solenoid rabbit hole gets me anywhere, if not have also sent along your words about fuel system crud.

 

Replacement of the solenoid as mentioned above seems to have done the trick. Car running great now. Installed this one, obtained from Mikey's Rotary.

 

Glad you got it sorted. Thanks for reporting back!