[J40sx]

1990 fastback
has around 59,XXX miles (original)
completely stock motor

My car rattles when i start it up, must be that infamous timing guide that is being chewed up, it only rattles for less than a second!

I first noticed something different about my car when it started
to jerk excessively. So i have to add tons of gas to stop the jerks.
Then the idle started to act up, i would start it up cold in the morning
usually the rpm goes up to 1,200-1,300 around there and last a while to warm up the engine, now it just shoots up for less than a second then it just goes down to 900 rpms.
After a short drive, it starts to idle at 800rpms.

The other problem:
I was at a car meet and my car just suddely dies when i try to start it.
There are plenty of cars around so i jump start my car and it works perfect. I leave it on so the alternator can juice up the battery. Afterwards i turned it off. Later on cops decided to raid the meet, so everyone is leaving, then i started my car, and nothing, would not start. I even asked the cops to help me start my car, does bastards just dicthed me and said call a "tow truck" so i was by myself for a second, friends showed up, and jumped start the car, works as soon as the head lights are turned on it dies, so i got a new battery.
A month later the car does not start after a day and a half without driving.
Its a new battery immposible!!!
I noticed a cranking noise couple days before, when i would start the car, not it won't start at all.

Any clues?
jump the battery agian?
bad alternator?
Clean the MAFS and IACV?

i will try to figure this out tom

thanks