I have a 1976 Fiat 124 Spider.  

When I start the car, instead of a nice even purr, it sounds a bit
like a tractor.  The sound is sort of like the sound it used to make
in the winter when it hadn't warmed up yet.  The engine is basically
occasionally cutting out and then re-starting, in little bursts.  Or,
that's how it sounds.  And then when I try to drive it, it lurches
hideously.  And then it sometimes dies.

This is a recent development, and the only thing that's happened to
the car that could be a cause of this is that it recently overheated,
and it's been raining a bit (I live in Boston).  The car has been kept
outside.

I have this suspicion, that might have come from a recent dream, that
this has something to do with the spark plugs.  But really I know
nothing about cars and have thus far been unable to locate the spark
plugs.

So the question is: what is the probable cause of this tractor-like
behavior?

Hi, you might need to clarify if you'll be happy with some
speculation. I used ot have a very similar car (it might have been a
74, it's been a long time). It would be hard to answer well without
some diagnosis.

You give two clues. Let's start with the bad one: overheating. Did it
lose it coolant in the process? You might have warped the head, and so
are not getting a good seal, and this leads to what you describe more
or less (that is, it makes it run terribly, if at all). I would have
someone check your head gasket. If you are lucky they can replace that
and make it fit tight. If not, that's gloom and doom. Hopefully it
isn't warped!!

Second, the rain. Now, what about an old fashioned tune up?? If you
have other reasons to suspect the spark plugs, go there, but it
doesn't sound like it from here! Changing (or just cleaning) the plugs
is cheap, though, and I'd change (or at least clean well) the wires
and cap if you have ruled out head problems. It should have points and
they are always a good thing to change, too. All this is routine tune
up stuff. Cross your fingers.

You need a mechanic! Good luck. Let us know if this helped at all.
LMNOP-ga

I don't think any coolant was lost in the process, but I am not 100%
sure of this.  I didn't see any green fluid on the ground afterwards.

Here are a few photos of the engine I took last night.  I don't know
if they are helpful in clarifying the situation at all.

http://nat.org/photos.php3?s=engine

I used to own a 1978 Porsche 914, wonderful car. I had a similar
problem, but not identical. Could it be either the carburator itself,
or possibly a new type of gas you're using, too rich, or lean?

If you can find a product called " fuel set " at your local car bits
supplier, try it according to instructions on the 500 ml. bottle. I
used 10ml. per 10 litres of unleaded fuel plus a couple of capfuls of
upper cylinder lubricant in my old  79 model Holden [G.M.] Gemini work
van. The old girl ran like a swiss watch right up to the time i sold
her as a licensed running knockabout vehiclem, for $300. I also used
this product in my early model two stroke outboard motor , Many of the
problems that mechanics say they solve by replacing spark plugs, can
be caused by crook fuel, contaminated by either water or too high
level of additives. I never had to change the plugs in the Gemini for
the three years I owned it, although all the books say you MUST. Saved
a few coins along the way. Try it, You cant go wrong.

Water in the gas tank can also make a car do that - used to happen to
my old 1978 Fiat.

Hi again,
Thanks, but the pics don't really help. And if you never lost fluid,
you probably didn't overheat to the point of damaging the engine. Who
knows for sure. I'd go back to the rain affecting the cap, coil, and
wires, and your first step is free: wipe them all down one by one,
including inside the cap. Seems like a pain but just takes 5 minutes
and some rags. And knowing what the parts are. As for additives, won't
hurt, but probably not (in my experience) your first step...you can
spend a lot adding things willly-nilly like that. Having said that,
the water in the tank is a 99 cent fix with isopropanol (dry gas).
Anyway, I guess you need to post a sound recording of it next! Just
kidding. Good luck. LMNOP-ga

Hi. Any luck??
LMNOP-ga

I had one in 1980. It developed a number of bizarre problems that they
never seemed to be able to fix quite right. If memory serves me, it
was some sort of on-board computer problem. The problem was that at
that time not many mechanics knew a great deal about on-board
computers.

I solved my problem by selling it. It never bothered me again.

tutuzdad-ga

I'M SURE I HAVE THE ANSWER TO YOUR QUESTION I'LL TELL YOU TOMORROW
BECAUSE I GOT TO GO I'M IN A PUBLIC COMPUTER.