I'm still having intermittent problems w my 79 12a w 25K miles. it ran fine for a month or so but having problems again, just runs bad with backfiring, no power, wont idle. carb is good, the only clue I have is that the tach bounces erratically when it runs bad. I'm thinking ground problems, already replaced battery/starter ground cable, not sure where all the other grounds are.

 

Have you changed the fuel filter lately? Checked the fuel pump for proper pressure?

 

Have you changed the points, cap, rotor, plug wires? These are normal wear items and can age out also.

How long as it sat? The fuel filter can clog and the tanks and get really rusty from sitting a few years.

 

all that stuff has been done w less than 4k on it. tank cleaned and coated, new pump, filter, hoses, points, plugs, cap, wires, battery, condensers, etc. all new, rebuilt carb. the tach bouncing whenever it acts up makes me think it's an electrical problem. and because it's intermittent and will go away for awhile, run great and then the problem comes back. I also swapped out the trailing coil, and that made no difference.

 

Get a new gas cap. Mine did that whenever i didn't drive it for a few days.

 

The backfiring makes me think timing is slipping since it runs ok for a while.

 

tach bouncing = ignition not being right, which is probably the points

 

gas cap? really? timing slip? how could that affect the tachometer? and how could it slip? it's bolted down tight

 

My gas cap was bad and I had my tach bouncing and engine fumbling every time I let the car sit for a few days . I suspect air or moisture would get into the system and after driving it tor a bit it would purge itself. Worth a try since you say you have changed everything else as I did .

 

OK, but that's not what's happening. It will work fine for a month, then for no apparent reason it starts this **** and will act this way for some time: days, weeks whatever. then it's ok for a while, and runs great

 

Sounds electrical . Have you checked for vacuum leaks ? A vac line may be loose .

 

This is probably really a stretch, but maybe one of the ignitors is going bad. I lost an ignitor years ago, which resulted in loss of the tach signal and the fuel pump operation. It stopped the car on me a couple of times, but then would restart again after some cooling down and would then seem fine for a period of time. Maybe your signal is more erratic, causing an on again off again situation. The '83 wiring diagram shows a wiring coming off the trailing ignitor. Not sure if that is the same for the SA. I don't know how the ignitor affects the fuel pump, since I can't see a direct connection in the wiring diagram, but it definitely caused my fuel pump not to work when the ignitor was on the fritz. Maybe it is through the ECU?

Good Luck

Carl

 

The 1979 has point and no ignitors. Maybe a bad dizzy gear since you said it wasn't the points.

 

Oops! Too much of a stretch I guess ;-)

Carl

 

Could it be weather related somehow? Have you noticed any correlation between heat / humidity and how it runs?

 

I don't think so, it seems the longer/further I drive it the more likely that it happens, so (I think) that could be from something bouncing loose or getting hot. or it could just be random
going to check points/dist, vacuum, going to clean every connector and connection I can find and maybe change the gas cap

 

When the tach is bouncing erratically, are you applying throttle and watching the tach jump around? When it does this, does it sound as though the engine has a rev limiter? Does it do this on first start with the engine cold only?

 

yes

no, but it has a lot of trouble revving

no. but when it does I know I'm in for a rough ride

 

I know this is a long shot, maybe the pilot bearing.

 

Out of curiosity , how would that cause issues ?

 

The motor can rev but not respond to speed/RPM increases. The tach however would appear to work properly. I'm just trying to think of other things since the OP seems to have covered all the other possibilities and says those things are fine. My bet is still the dizzy though.

 

That issue would surely get worst .
In other news , My gas cap fix didn't entirely clean the issue up. RIp engine .

 

after thoroughly checking ignition system points, coils, battery, etc good spark at plugs, 13v at pos coil terminals, swapped coils, fusible links good, it was running ok for a while, then yesterday started acting up again, checked everything again, no change, I suspected the ignition switch might be a problem after seeing posts about how they are known for deteriorating, so I worked the switch a bunch with the battery disconnected, and the problem seemed to get worse, now the tach barely works at all, still bounces some but mostly doesn't work, car still runs but doesn't like to rev much still. question is does the tach signal go through the ignition switch? if so that could be the problem maybe? reluctant to pull the switch and take it apart if I don't need to, but maybe I should?

 

The tach gets its signal from the trailing negative, but, with that said, both tach positive signals do go through the ignition switch.

 

disassembled, cleaned and reassembled ignition switch, lubed w electrical grease, no difference, if anything ran worse. dropped it off at a shop because it wouldn't make it home, hopefully this guy can find something, apparently he's doing a 2nd gen of his own so isn't a stranger to rotaries. mechanics are retiring in my town so there aren't many options to have auto work done here, but I'm hoping for the best.