1995 sonata problems

my alternator died recently, I lost all power on the road, the engine still
worked while I was giving it gas except very low acceleration at first (I
thought the transmission had died).

after alternator was fixed, the first few times I turned the engine on, at
idle, the RPM swung widely between 1000 and 2000 RPM. after backing out of
the driveway (smooth reverse) and putting it in drive, the first time I
accelerated forward, the acceleration was very rough and abrupt.

now these symptoms are gone, but motor sometimes vibrates at idle and RPMs
at idle oscillates quite fast around 750RPM (let's say it goes fast between
730 and 780 RPM)

this didn't really happen before (or maybe I started nottincing things
better after getting stuck in the middle of the road)

what could be the cause of this? could the engine control system have been
damaged?

 

You have fouled your spark plugs when the weak battery wasn't able to
generate reliable spark.

 

uhuh... ok, I assume sparkplugs are something that's easy enough to change
without going to the dealer? cause we've sunk 1000 bucks in this car in the
past month, first the water pump now the alternator...

what kind of sparkplugs does the sonata use? standard, or does it need
specific ones? is there anything I should be aware of, or just buy some
plugs and pu them in?

 

I meant fouled in an insignificant way. They arent wrecked.
If thats the cause of the trouble they will come clean with driving - eg run
the engine to 3000rpm for a a few minutes. get a descent flow of hot
exhaust gases and things come clean.

 

That all depends on what engine you have. The I4 plugs are relatively
simple to change. You'll need to remove the valve cover and then
unscrew each plug. Replace each with the appropriate plug according
to your owners manual (not all spark plugs are the same, they come in
different shapes and heat ranges). If you don't have a torque wrench
then tighten each plug by hand and then tighten them an additional 3/8
of a turn with a wrench. Make sure you don't mix up the plug wires
when reinstalling them.

If you have the V6 you'll need to remove the intake pipe, throttle
body, and upper intake manifold, as well as valve covers. I'd
recommend taking it to a shop to have the plugs replaced unless you've
spent quite a bit of time under the hood.

 

it's an I4

what happens if I mix up the wires when putting them back on?

 

It won't be good. Keep them in order. The best way is to label them
with tape or to only change one plug at a time.