My car is acting like it wants to die, I need to know what could cause this?

I've just changed my wires and and everything is just fiiiiiineeeee :). I don't know exactly if the engine was missing or vibrating but thanks to you I saw that motor mount and the cat are ok (I had no idea about those parts before)so today I've changed the spark wires and my engine works smooth.

Engine Mechanical problem
2001 Saturn SL1 Automatic

starts but will not stay running but one or 2 sec but will not continue to run,

has gas, & battery is good, has 70,000 miles, clean air filter, & fresh oil change

My SL1 makes a horrible rattling noise (sort of like the valves are shuddering in their seats, maybe?) When I first start it for the day. All fluids are full, and there's no history of burning oil. Lately, on top of the rattle (which, by the way, is worse if I'm on a hill or if it's cold out), it requires me to up the RPMs over 3000 for about 30 seconds, or it dies. Once it gets going, the car runs great, although the gas milage isn't what it used to be. But the rattle is making me crazy.I'm terrified I'm going to throw a rod or something.

But wouldn't the SES or Check Engine light come on? Very occasionally, the low radiator fluid light comes on, and then goes out after about a half mile. And it doesn't run rough, nor does the idle fluctuate (although it does when the A/C is on for a while.)

I checked all the fluids this morning, and yeah, the coolant overflow is a little low. But that's easily fixed. The sound just comes from the engine. Hard to pinpoint where, exactly. I even checked the mounts, and they're all solid. The noise stops after I get going, though. Unless I'm backing down my parents' driveway (I'm going slow, and it's a steep hill), and then it lasts until I get off their driveway and onto the flat road.

Saturn SL1 2001 manual

I've been having random high idle for a year. Would happen every time I started the car cold. Would happen about 50% of the time during driving when clutch is depressed. Most of the time at around 2000 and occasionally more up to instances of 3000+. Maybe it would go higher, always shut it off when it tries that. Only way to bring it down is to turn car off and restart. This past week it's been out of control. Occuring almost 100% of the time clutch is depressed. Shutting off still works but now it comes right back. Tonight, after driving all day and then sitting in parking lot for about 4 hours, I started her and drove a couple of miles in town to a drive-through, where I had to shut her off and restart her to kill the high idle. About a minute later the idle bottomed out and tried to die. Tried to catch her but lost her and almost couldn't get her restarted. Had to feather the gas because simply depressing the pedal would make it die. Now at the beginning of every gear she will buck and try to die if I attempt to give it gas at all. I made it home by letting her accelerate herself up through the gears. I could give her some gas at the upper part of each gear and shifting up late would help get passed the lower ends but from a stop, getting through the first 3 gears takes forever. Took it to Autozone and here are my codes:

P0172
P0300
P0442

What just happened to her today? She's practically undriveable as of tonight.

I have, and it's not. But I'm going to take it somewhere and get the codes read and see what's up. I'll post them when I get them.

No codes came up at all. Rats. But this morning, it took 3 tries to start it (the third time, I put my foot on the gas up to 2000 rpm for about 2 minutes before it took). Radiator light came on during that time. And when I stop, it revs to about 2000 rpm twice. When I put it in park, it revs up to 3000 for about 20 seconds, then falls. I'm still thinking it's either an idle sensor or, as you say, saturntech9, the coolant temp sensor. I'm going to try disconnecting the battery for a while, see if things reset?

I have a 2001 SL1 Saturn. The car wasn't going into reverse, so I found another transmission and changed it. Now, it stalls when I put it into drive. I've checked the shift solenoids and they were fine. Connections are fine. I flushed the cooling system (even though that has nothing to do with the transmission). I checked the codes and nothing was showing up.

I'm lost. Any ideas?