My A12 has been running very poorly when cold. But when it fully warms up it runs perfect. It idles just fine, but at part throttle it misses and sputters. I find myself driving pedal down, pedal up. Heavy throttle runs fine, but anywhere in between is bad.

A few days ago on the way to work it was so bad I had to pull over, and looked in the engine compartment. There was moisture dripping everywhere (though it was a sunny day, it is winter in Seattle). I noticed that the distributor cap had a film of road grime on it. I wiped it off with some paper towels, and it instantly ran better and I was able to make it to work.

However, even after cleaning it, it still runs not so great when cold. I've checked the timing and dwell and they are spot on. I think this is the 'ole distributor cap moisture problem.

Here's a suggestion for anyone experiencing poor running: clean the distributor cap with dish soap and water, inside and out. Scrub any grime off of it (inside and out). Then let it thoroughly dry. It makes a big difference when the weather is damp.

I'm currently getting almost the same hassle with my 120Y. I've pulled the DGV weber off and made sure it was clean (which it was) and all plugs, points, etc are spot on. I'm now looking at spark as well, but I'm also wondering if it could be the vacuum advance unit ?

just try a nother coil DD (you konw is in good condition), as coils can do very strange and wierd things if they are on the way out

Hmmm ... I'm getty very bad fuel economy as well. And lastly, #4 spark plug terminal in the cap is oxidized (indicating #4 has been missing). The funny thing it that it runs great when warmed up.

I've got an electronic ignition coil and distributor. I'm going to put that on and see how it works.

DD, let me know how you get on as it might help me track down my own problem.

I'll also try the new dizzy cap/ coil as well

Thanks, B120dat. I hadn't thought about the coil possibly being bad.

anb008, it's very rare that a cap needs replacing. 90% of the time they just need cleaning. After you clean the cap, inspect it for black carbon "tracks" (burn marks) between any two terminals (inside or out). Replace it if it has these.

The coil is different, it's hard to tell if it's bad by looking at it. You can measure resistance, but you'll need specs. The best thing to do (to not waste money) is to borrow one of another car, even a Ford or GM coil will work fine if it is the same type (pre-electronic, and uses the ballast resistor). If that clears up the problem, then by all means by a new coil.

try wiping yoursprk plug porcelains.If theyare dirty enough it can short the plug and cause ####y running.

How's this for something from left field ??? Mine was a case of a bad batch of fuel...
I filled the tank over the w/end and almost instantly everything was fine.... Something for future thought...

But I'll still do the usual checks !

Distributor caps & rotor buttons are cheap & should be regarded as a service consumable, so if you suspect these parts, just replace them. The nice smooth glossy surface inside & out is less condusive to moisture retension [like oxidised paint versus a shiney new wax job]

Somehow, i suspect that the electrics, even if less than 100%, might just be a red herring. Check your carb too as it might just be running lean when cold. Full operating temp often brings the bad running to an end.
You know the usual suspects, warm air to the carb [when fitted] no manifold heat, impared accelerator pump function, faulty choke function. The usual stuff.

Humid days or when it's cold enough for concentration to be all over your cap etc. is hell on a cracked distributor cap as well. You may not see a cracked distributor cap right away but this could be the problem you were experiencing and it may come back another day when moisture is present.