2003 monte Carlo won't run
 

Help.... My 2003 monte Carlo won't crank. It sounds like it's huffing and puffing and then it let's out a big puff. It's not getting gas, I don't think.

Where is this "puff"? Is there a color or smell to this "puff"? How do you know it's not getting gas? Which engine is it (the 3800 or 3400)? Won't crank, so the starter is not engaging?

Nothing but shots in the dark without proper data. Check fuel pressure or even live data as youre trying to start it.

I dont understand how it can make puffing sounds tho, without cranking.

If you want to "throw parts at it", start with the IAC and MAF. -But thats not the recommended route and forget that if its indeed not even cranking. In that case, get the battery tested. Check the fuel pump.

If its truly not cranking AND you have no fuel pressure you may have an electrical issue. If it were a fuel problem, it wouldnt stop the engine from cranking. If something was preventing the engine from cranking, it wouldnt shut down the fuel pump.

it's the 3400. We got it to crank but it didn't stay running long. It had a rough idle and then it went dead and now all it will do is turn over

If it turns over, it is cranking, engine is not seized, so that is good.
Sadly, you are giving vague details to provide much help. But I will run through a bunch of things.

- Check for any engine codes or pending codes?
- Verify the air filter is clean?
- Check for spark?
- Listen if the fuel pump engages when you turn the key? Check for fuel pressure?
- Verify if the security light remains active after a failed attempt to start?
- Check for evidence of coolant in the oil?
- Check if the cooling system will hold pressure?

The last item could be your important one. When you mentioned that it let out a big puff, that is not descriptive enough. WHERE? Was this a cloud of smoke from the exhaust? What color, did it have a smell.

Potential theory: bad head and/or intake gaskets.
If either one failed and is letting coolant make it's way into the cylinder, it could make the car hard to start AND rough idling until all the coolant blows out of the problem cylinder. Plus, the coolant could create clouds of steam out of the exhaust (white smoke). It might not be starting because there is now too much coolant in one or more cylinder. To figure out this problem, I would consider two things:
- Pressure testing the cooling system (most parts stores will do a free loan-a-tool program to get the "radiator pressure tester"). Try to pressurize the system. If it does not hold OR won't even build up pressure, inspect for leaks (listening for hissing and looking for possibly bubbling/dripping of coolant somewhere). Can also take the oil cap off and listen for issues there.
- Remove the spark plugs, find out if they are wet (right now, specifically looking for signs of coolant).

Those two tests will narrow down to head and/or intake gaskets.