I have a 2005 Monte Carlo LS, 3.4 or 3.6 V6 i believe.
~130k miles

It's happened 5 times so far, and occurring far more frequently. First of all, it's struggling to start at all. sometimes i have to give it gas for the engine to even start. Then, it has a very rough idle. And now, the engine shuts off while i'm driving either up hill or while turning. the electronics stay on, but the engine is suddenly off. The spark plugs are brand new. The oil is changed religiously. I'm guessing it's the fuel regulator valve or fuel filter, but I honestly have no other ideas. any advice would be greatly appreciated.

 

Check engine light coming on at all, or have you scanned it for codes?

You can check the fuel pressure at the rails (there's a schrader valve to hook a gauge up to in the engine bay) to rule out the pump or filter (although if you're still on the original filter at 130k miles it would be worth changing regardless).

Is the car struggling to start every time, or is that an intermittent problem? Same question for the rough idle.
If it is every time, I'd start looking for a vacuum leak.

 

i haven't checked for new codes lately. the rough start and idle is every time, not just occasionally.

if it is a vacuum leak, what's the best way to track down the source?

 

Check all of the vacuum lines and connections in the engine bay, make sure that everything is connected correctly and that the lines aren't cracked at all.

You can also spray carb cleaner along possible leak sites with the car idling, when the carb cleaner gets sucked into the leak the idle will noticeably change.

 

To add to that, if you have a vacuum guage, you can get a read on the vacuum system and see if there is a problem that way.

I'd change the fuel filter and if you don't know the age of the air filter change that (if the car has trouble getting fuel or air, can cause big problems).

You mentioned the plugs are brand new, how about the plug wires? If those are still original, the sheething could be weakening and promoting possible arcing.

Also, the more important question, did this condition start immediately or shortly after changing the plugs? If so, you could have bad plugs. Also, what brand plugs? If you say Bosch, change'em. My experience with Bosch plugs (along with many others) is they will not serve long or properly in a GM engine. I'd stick with AC Delco (except, last 3400 I changed plugs on, I used NGK and learned while changing the plugs that factory original AC Delco plugs were really NGK plugs, was scribed in the metal and AC Delco stamped on the stem).

 

Can you pop the MAF sensor switch off the MAF and try to start the car and see if it isn't as rough.

 

no the plugs have been in for about 6 months now. Last night I changed the IAC valve and the fuel filter and the problem remains. While it rough idles the cluster lights flicker, could this an electrical issue? the only other thing I know to do, as suggested by biggriggs, is to check the vacuum lines. it's getting freaking annoying!

 

Here’s what I’ve done so far-
new MAP and IAC sensor. Cleaned the MAF as it was less than a year old. Thought I had gotten bad gas so pulled the changed the fuel filter, pulled the pump, cleaned it and the tank, fuel pressure reads 48 without engine running, 40 with- appropriate according to specs of 48-55psi, with a 3-10psi drop in running position. New plugs and plug wires- that #6 is a Bi*#h! I tried to check for vac leaks- spraying starter fluid while running especially beside the brake fluid fill where it was mentioned in another thread is a problem site. Although the car is running much better- it will start and run at about 800rpm, but after it warms up- about a 20 min drive- it will still stall at stop signs and turns, but at least now it will start right back up. I’m wondering if fuel pressure is getting low while driving...found replacement pump for $55 from A1 auto...any pros or cons about that merchant?
chasing my tail here...throws no codes. No engine light...gonna adjust the idle screw to 1000rpm and see if that helps for now. Any advice appreciated!!

 

I think there is a fuel pressure regulator that causes the explosions on the 6th Gen Monte Carlo with 3800 motor you might want to check that.

 

Could the cat be plugged up? Might help to clear up if its the 34 or 38 also. Could you have got some vac lines mixed up?