Bad idle
 

Okay so I have a new issue. My car was running fine about 2 weeks about and then randomly it starting idling bad and would stall at idle. I checked spark plugs, wires are brand new. I triple checked the fuel pump(being that I just replaced it). And today I changed the maf thinking that was the issue. Anyways I threw the new maf on car started and didn't die at all I drove it, and it responded well to the new maf. As I am getting to work it starts idling bad again. I thought nothing of it and went into work. Going on break I drove the car home and the whole way it was idling rough to the point that at a dead stop I would have to put it in neutral to keep it alive. I am gonna put fuel line deice in there tonight. But I pretty much think it is the fuel system somewhere. Any ideas or help?????

Vacuum lines. The stock lines are relatively cheap and tend to dry up very easily over time. I'll bet if you went out and rubbed one of them between your fingers, it'd crumble to dust with a slight touch cuz it sounds like you haven't touched them at all in figuring out this idle issue. Go get some replacement line, either silicone or OEM tubing and swap em out, I'll bet it fixes your issue to near perfection. The only other thing it might be if that doesn't do it is a dirty EGR valve or throttle body, but my money's on vac lines just cuz of how notorious they are for being incredibly brittle after a good period of time. What motor do you have?

i4 or v6? Did you change the fuel filter? Yes, it could be a vacuum line. Do you have a check engine light?

I have been having the same issue. I am replacing the vac lines tomorrow as soon as I know where the vac lines are on my car, lol.

1.8T or 2.8?
a bad idle could also be the TIP falling off. my issue use to be at the turbo inlet.

http://img9.imageshack.us/img9/1645/vaclines.jpg

The vac lines are the bright green things I've highlighted in this generously google-donated picture (too dark to go snap a pic of my own, though its not all that different haha so whatev) Basically, just replace any hose that looks like its made of that same hose that you can see. Obviously, I couldn't highlight all of them, just their general locations, but it should be enough for you to know where to be looking. The ones I highlighted on the two sides of the intake runners are plastic and, if you're careful, shouldn't need to be messed with unless visibly cracked or you have enough line to make both of those runs with the rubber hose. I highlighted those to show the less obvious places to look, as the plastic lines more or less just run over the sides of the intake runners, but there is rubber hose on the ends of them where they connect to the rest of the system. Good luck!

And you told me before that the vac lines are 5/8" right?

NO! Waaaay too big, that's over 15mm. The lines will be metric, and I'm pretty sure they're 3.5mm. And you'll want to stick with a metric measurement because even that fractional difference between the conversion can mean the difference in it being a tight fit like it's supposed to and it being just loose enough to pop off under pressure. 3.5mm =~ .137795276 inches, which is somewhere between 1/8" and 9/64", so you can see that you'll never quite have that perfect accuracy, it'll either be too small to fit onto the connectors, or too big to stay, so definitely stick with the metric measurement.

I have the v6 motor and I will replace vacuum lines next chance I get. I do not have a check engine light of at the moment

fuel filter was changed about 7k ago